Issue #1244: Utils functions updated according to the Effective Dart Guide, relative tests updated accordingly.
diff --git a/Language/Libraries_and_Scripts/Scripts/top_level_main_t01.dart b/Language/Libraries_and_Scripts/Scripts/top_level_main_t01.dart
index fc26d1f..6387547 100644
--- a/Language/Libraries_and_Scripts/Scripts/top_level_main_t01.dart
+++ b/Language/Libraries_and_Scripts/Scripts/top_level_main_t01.dart
@@ -16,7 +16,7 @@
 run_main() async {
   String executable = Platform.resolvedExecutable;
   String eScript = Platform.script.toString().replaceAll(".dart", "_lib.dart");
-  if (isAOT) {
+  if (isAot) {
     // This is the case of AOT configuration
     executable = executable.replaceRange(
         executable.lastIndexOf(Platform.pathSeparator) + 1, null, "dart");
diff --git a/Language/Libraries_and_Scripts/Scripts/top_level_main_t06.dart b/Language/Libraries_and_Scripts/Scripts/top_level_main_t06.dart
index 689e9c2..486c6cb 100644
--- a/Language/Libraries_and_Scripts/Scripts/top_level_main_t06.dart
+++ b/Language/Libraries_and_Scripts/Scripts/top_level_main_t06.dart
@@ -16,7 +16,7 @@
 run_main() async {
   String executable = Platform.resolvedExecutable;
   String eScript = Platform.script.toString().replaceAll(".dart", "_lib.dart");
-  if (isAOT) {
+  if (isAot) {
     // This is the case of AOT configuration
     executable = executable.replaceRange(
         executable.lastIndexOf(Platform.pathSeparator) + 1, null, "dart");
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t001.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t001.dart
index d7026e7..ad35ce6 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t001.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t001.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Object> {}
-class C extends CHECK_TOP_MERGE<Object> {}
+class B extends CheckTopMerge<Object> {}
+class C extends CheckTopMerge<Object> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t002.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t002.dart
index ae55ab6..638a491 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t002.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t002.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Object?> {}
-class C extends CHECK_TOP_MERGE<Object?> {}
+class B extends CheckTopMerge<Object?> {}
+class C extends CheckTopMerge<Object?> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t010.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t010.dart
index d4c37a0..3bff62c 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t010.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t010.dart
@@ -19,8 +19,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Object?> {}
-class C extends CHECK_TOP_MERGE<dynamic> {}
+class B extends CheckTopMerge<Object?> {}
+class C extends CheckTopMerge<dynamic> {}
 
 class D1 extends B implements C {}
 class D2 extends C implements B {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t011.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t011.dart
index 9343dde..cf5974d 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t011.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t011.dart
@@ -19,8 +19,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Object?> {}
-class C extends CHECK_TOP_MERGE<void   > {}
+class B extends CheckTopMerge<Object?> {}
+class C extends CheckTopMerge<void   > {}
 
 class D1 extends B implements C {}
 class D2 extends C implements B {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t015.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t015.dart
index 1408b32..d4841d6 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t015.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t015.dart
@@ -19,8 +19,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<int> {}
-class C extends CHECK_TOP_MERGE<int> {}
+class B extends CheckTopMerge<int> {}
+class C extends CheckTopMerge<int> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t017.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t017.dart
index 22b25b4..0e6da6a 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t017.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t017.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<int?> {}
-class C extends CHECK_TOP_MERGE<int?> {}
+class B extends CheckTopMerge<int?> {}
+class C extends CheckTopMerge<int?> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t036.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t036.dart
index 9ce2e01..a8e796d 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t036.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t036.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Function?> {}
-class C extends CHECK_TOP_MERGE<Function?> {}
+class B extends CheckTopMerge<Function?> {}
+class C extends CheckTopMerge<Function?> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t037.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t037.dart
index b48318b..857f400 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t037.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t037.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Function> {}
-class C extends CHECK_TOP_MERGE<Function> {}
+class B extends CheckTopMerge<Function> {}
+class C extends CheckTopMerge<Function> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t039.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t039.dart
index d8392de..562900b 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t039.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t039.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<dynamic> {}
-class C extends CHECK_TOP_MERGE<dynamic> {}
+class B extends CheckTopMerge<dynamic> {}
+class C extends CheckTopMerge<dynamic> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t042.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t042.dart
index dd27e51..303f0d5 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t042.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t042.dart
@@ -19,8 +19,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<dynamic> {}
-class C extends CHECK_TOP_MERGE<void   > {}
+class B extends CheckTopMerge<dynamic> {}
+class C extends CheckTopMerge<void   > {}
 
 class D1 extends B implements C {}
 class D2 extends C implements B {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t048.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t048.dart
index 7f031df..4a57595 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t048.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t048.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<void> {}
-class C extends CHECK_TOP_MERGE<void> {}
+class B extends CheckTopMerge<void> {}
+class C extends CheckTopMerge<void> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t057.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t057.dart
index fd27fe1..174695e 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t057.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t057.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Null> {}
-class C extends CHECK_TOP_MERGE<Null> {}
+class B extends CheckTopMerge<Null> {}
+class C extends CheckTopMerge<Null> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t062.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t062.dart
index 4d34639..716f543 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t062.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t062.dart
@@ -19,8 +19,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr> {}
-class C extends CHECK_TOP_MERGE<FutureOr> {}
+class B extends CheckTopMerge<FutureOr> {}
+class C extends CheckTopMerge<FutureOr> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t064.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t064.dart
index 7e0f327..2dece33 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t064.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t064.dart
@@ -20,8 +20,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr> {}
-class C extends CHECK_TOP_MERGE<Object? > {}
+class B extends CheckTopMerge<FutureOr> {}
+class C extends CheckTopMerge<Object? > {}
 
 class D1 extends C implements B {}
 class D2 extends B implements C {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t067.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t067.dart
index 2d029a6..b61bde7 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t067.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t067.dart
@@ -20,8 +20,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr> {}
-class C extends CHECK_TOP_MERGE<dynamic > {}
+class B extends CheckTopMerge<FutureOr> {}
+class C extends CheckTopMerge<dynamic > {}
 
 class D1 extends C implements B {}
 class D2 extends B implements C {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t068.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t068.dart
index dbc600c..eb62f83 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t068.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t068.dart
@@ -20,8 +20,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr> {}
-class C extends CHECK_TOP_MERGE<void    > {}
+class B extends CheckTopMerge<FutureOr> {}
+class C extends CheckTopMerge<void    > {}
 
 class D1 extends C implements B {}
 class D2 extends B implements C {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t075.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t075.dart
index b33b47a..7059362 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t075.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t075.dart
@@ -19,8 +19,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr<int>> {}
-class C extends CHECK_TOP_MERGE<FutureOr<int>> {}
+class B extends CheckTopMerge<FutureOr<int>> {}
+class C extends CheckTopMerge<FutureOr<int>> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t076.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t076.dart
index bfe3615..6729c07 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t076.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t076.dart
@@ -19,8 +19,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr<int?>> {}
-class C extends CHECK_TOP_MERGE<FutureOr<int?>> {}
+class B extends CheckTopMerge<FutureOr<int?>> {}
+class C extends CheckTopMerge<FutureOr<int?>> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t077.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t077.dart
index 9f76fcf..ed09133 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t077.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t077.dart
@@ -19,8 +19,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr<FutureOr>> {}
-class C extends CHECK_TOP_MERGE<FutureOr<FutureOr>> {}
+class B extends CheckTopMerge<FutureOr<FutureOr>> {}
+class C extends CheckTopMerge<FutureOr<FutureOr>> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t089.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t089.dart
index cf77e9e..42aabc3 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t089.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t089.dart
@@ -20,8 +20,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr<FutureOr>> {}
-class C extends CHECK_TOP_MERGE<dynamic>  {}
+class B extends CheckTopMerge<FutureOr<FutureOr>> {}
+class C extends CheckTopMerge<dynamic>  {}
 
 class D1 extends B implements C {}
 class D2 extends C implements B {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t092.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t092.dart
index 10299ff..6468f3c 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t092.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t092.dart
@@ -20,8 +20,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr<FutureOr>> {}
-class C extends CHECK_TOP_MERGE<void>  {}
+class B extends CheckTopMerge<FutureOr<FutureOr>> {}
+class C extends CheckTopMerge<void>  {}
 
 class D1 extends B implements C {}
 class D2 extends C implements B {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t097.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t097.dart
index 2f29c34..23dff9a 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t097.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t097.dart
@@ -18,8 +18,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Function?> {}
-class C extends CHECK_TOP_MERGE<Function?> {}
+class B extends CheckTopMerge<Function?> {}
+class C extends CheckTopMerge<Function?> {}
 
 class D extends B implements C {}
 
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t102.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t102.dart
index 7afd60a..6835d28 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t102.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t102.dart
@@ -20,8 +20,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<FutureOr> {}
-class C extends CHECK_TOP_MERGE<FutureOr<FutureOr>> {}
+class B extends CheckTopMerge<FutureOr> {}
+class C extends CheckTopMerge<FutureOr<FutureOr>> {}
 
 class D1 extends B implements C {}
 class D2 extends C implements B {}
diff --git a/LanguageFeatures/nnbd/overriding/override_checking_A06_t119.dart b/LanguageFeatures/nnbd/overriding/override_checking_A06_t119.dart
index 3a927c0..9a79e70 100644
--- a/LanguageFeatures/nnbd/overriding/override_checking_A06_t119.dart
+++ b/LanguageFeatures/nnbd/overriding/override_checking_A06_t119.dart
@@ -19,8 +19,8 @@
 
 import "../../../Utils/expect.dart";
 
-class B extends CHECK_TOP_MERGE<Never> {}
-class C extends CHECK_TOP_MERGE<Never> {}
+class B extends CheckTopMerge<Never> {}
+class C extends CheckTopMerge<Never> {}
 
 class D extends B implements C {}
 
diff --git a/LibTest/async/Future/Future.delayed_A01_t01.dart b/LibTest/async/Future/Future.delayed_A01_t01.dart
index c886ea7..d181ab3 100644
--- a/LibTest/async/Future/Future.delayed_A01_t01.dart
+++ b/LibTest/async/Future/Future.delayed_A01_t01.dart
@@ -16,7 +16,7 @@
 
 void check(delay, value) {
   asyncStart();
-  new Future.delayed(durationMs(delay), () => value)
+  new Future.delayed(durationInMilliseconds(delay), () => value)
     .then((v) {
       Expect.equals(value, v);
       asyncEnd();
diff --git a/LibTest/async/Future/Future.delayed_A01_t02.dart b/LibTest/async/Future/Future.delayed_A01_t02.dart
index 25403a8..b04cc90 100644
--- a/LibTest/async/Future/Future.delayed_A01_t02.dart
+++ b/LibTest/async/Future/Future.delayed_A01_t02.dart
@@ -15,7 +15,7 @@
 import "../../../Utils/expect.dart";
 
 check(delayms, value) {
-  Duration delay = durationMs(delayms);
+  Duration delay = durationInMilliseconds(delayms);
   Stopwatch sw = new Stopwatch();
   asyncStart();
   sw.start();
diff --git a/LibTest/async/Future/Future.delayed_A03_t01.dart b/LibTest/async/Future/Future.delayed_A03_t01.dart
index 1de092a..0e8bdf8 100644
--- a/LibTest/async/Future/Future.delayed_A03_t01.dart
+++ b/LibTest/async/Future/Future.delayed_A03_t01.dart
@@ -14,7 +14,7 @@
 
 check(delay, value) {
   asyncStart();
-  new Future.delayed(durationMs(delay), () {throw value;})
+  new Future.delayed(durationInMilliseconds(delay), () {throw value;})
     .then(
       (v) {
         Expect.fail("Created future should complete with error");
diff --git a/LibTest/async/Future/any_A01_t05.dart b/LibTest/async/Future/any_A01_t05.dart
index 5e9acab..87f1892 100644
--- a/LibTest/async/Future/any_A01_t05.dart
+++ b/LibTest/async/Future/any_A01_t05.dart
@@ -30,5 +30,5 @@
     asyncEnd();
   });
   asyncStart();
-  new Timer(durationMs(200), () => completers[3].complete("value"));
+  new Timer(durationInMilliseconds(200), () => completers[3].complete("value"));
 }
diff --git a/LibTest/async/Future/doWhile_A05_t01.dart b/LibTest/async/Future/doWhile_A05_t01.dart
index abde38f..7ad0a48 100644
--- a/LibTest/async/Future/doWhile_A05_t01.dart
+++ b/LibTest/async/Future/doWhile_A05_t01.dart
@@ -21,7 +21,7 @@
 
   FutureOr<bool> f() {
     num++;
-    return new Future.delayed(durationMs(100), () => (num < N));
+    return new Future.delayed(durationInMilliseconds(100), () => (num < N));
   }
 
   asyncStart();
diff --git a/LibTest/async/Future/forEach_A01_t03.dart b/LibTest/async/Future/forEach_A01_t03.dart
index f159e46..97c805f 100644
--- a/LibTest/async/Future/forEach_A01_t03.dart
+++ b/LibTest/async/Future/forEach_A01_t03.dart
@@ -18,7 +18,7 @@
 
   dynamic f(element) {
     log.add(element);
-    return new Future.delayed(durationMs(100));
+    return new Future.delayed(durationInMilliseconds(100));
   }
 
   asyncStart();
diff --git a/LibTest/async/Future/wait_A01_t01.dart b/LibTest/async/Future/wait_A01_t01.dart
index b972c1e..66f10d9 100644
--- a/LibTest/async/Future/wait_A01_t01.dart
+++ b/LibTest/async/Future/wait_A01_t01.dart
@@ -31,7 +31,7 @@
 
   int i = 0;
   new Timer.periodic(
-      durationMs(50),
+      durationInMilliseconds(50),
       (Timer t){
         Expect.isFalse(futureCompleted);
         completers[i].complete(i);
diff --git a/LibTest/async/Stream/Stream.fromFutures_all_t02.dart b/LibTest/async/Stream/Stream.fromFutures_all_t02.dart
index 6a9e3ee..7a2cf26 100644
--- a/LibTest/async/Stream/Stream.fromFutures_all_t02.dart
+++ b/LibTest/async/Stream/Stream.fromFutures_all_t02.dart
@@ -16,7 +16,7 @@
 import "dart:async";
 import "allTests_A02.lib.dart";
 
-Stream<T> create<T>(Iterable<T> data, {bool isError(T x)?, T? defVal}) {
+Stream<T> create<T>(Iterable<T> data, {bool isError(T x)?, T? defaultValue}) {
   return new Stream.fromFutures(data.map((T x) {
     return new Future.value(x).catchError((_) {}).then((_) {
       if (isError != null && isError(x)) {
diff --git a/LibTest/async/Stream/Stream.fromIterable_A02_t01.dart b/LibTest/async/Stream/Stream.fromIterable_A02_t01.dart
index 2c57428..26a8577 100644
--- a/LibTest/async/Stream/Stream.fromIterable_A02_t01.dart
+++ b/LibTest/async/Stream/Stream.fromIterable_A02_t01.dart
@@ -33,7 +33,7 @@
   }, onError: (error) {
     events.add(error);
     // wait some time for additional (wrong) events
-    new Future.delayed(durationMs(500), () {
+    new Future.delayed(durationInMilliseconds(500), () {
       Expect.listEquals([0, 1, 2, 3, 4, 5, "done"], events);
       asyncEnd();
     });
diff --git a/LibTest/async/Stream/Stream.periodic_A01_t01.dart b/LibTest/async/Stream/Stream.periodic_A01_t01.dart
index aa09e32..d83ce15 100644
--- a/LibTest/async/Stream/Stream.periodic_A01_t01.dart
+++ b/LibTest/async/Stream/Stream.periodic_A01_t01.dart
@@ -14,7 +14,7 @@
 import "../../../Utils/expect.dart";
 
 void check(int periodMs) {
-  Duration period = durationMs(periodMs);
+  Duration period = durationInMilliseconds(periodMs);
   const int maxCount = 5;
   int count = 0;
 
diff --git a/LibTest/async/Stream/Stream.periodic_A02_t01.dart b/LibTest/async/Stream/Stream.periodic_A02_t01.dart
index de64c84..c3e1e89 100644
--- a/LibTest/async/Stream/Stream.periodic_A02_t01.dart
+++ b/LibTest/async/Stream/Stream.periodic_A02_t01.dart
@@ -13,7 +13,7 @@
 
 void check(int periodMs) {
   Stream s = new Stream<int>.periodic(
-      durationMs(periodMs), (computationCount) => computationCount * periodMs);
+      durationInMilliseconds(periodMs), (computationCount) => computationCount * periodMs);
   int count = 0;
   asyncStart();
   StreamSubscription<int>? subs;
diff --git a/LibTest/async/Stream/Stream.periodic_A03_t01.dart b/LibTest/async/Stream/Stream.periodic_A03_t01.dart
index 5b4e351..b469b2e 100644
--- a/LibTest/async/Stream/Stream.periodic_A03_t01.dart
+++ b/LibTest/async/Stream/Stream.periodic_A03_t01.dart
@@ -17,7 +17,7 @@
 
 void check(int periodMs) {
   String id = "s$periodMs";
-  Duration period = durationMs(periodMs);
+  Duration period = durationInMilliseconds(periodMs);
   StreamSubscription<int>? subs;
   int count = 0;
   asyncStart();
diff --git a/LibTest/async/Stream/Stream.periodic_all_t02.dart b/LibTest/async/Stream/Stream.periodic_all_t02.dart
index 3ae85e2..e7f9f37 100644
--- a/LibTest/async/Stream/Stream.periodic_all_t02.dart
+++ b/LibTest/async/Stream/Stream.periodic_all_t02.dart
@@ -12,7 +12,8 @@
 import "dart:async";
 import "allTests_A02.lib.dart" as all;
 
-Stream<T> create<T>(Iterable<T> data, {bool isError(T x)?, required T defVal}) {
+Stream<T> create<T>(
+    Iterable<T> data, {bool isError(T x)?, required T defaultValue}) {
   int count = data.length;
   Iterator<T> iterator = data.iterator;
   return new Stream<T>.periodic(
@@ -26,7 +27,7 @@
           }
           return x;
         }
-        return defVal;
+        return defaultValue;
       }
   ).takeWhile((_) => count >= 0);
 }
diff --git a/LibTest/async/Stream/any_A02_t01.test.dart b/LibTest/async/Stream/any_A02_t01.test.dart
index abe5eb6..3326369 100644
--- a/LibTest/async/Stream/any_A02_t01.test.dart
+++ b/LibTest/async/Stream/any_A02_t01.test.dart
@@ -19,10 +19,12 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   Object error = new Error();
-  check(create([error], isError: (_) => true, defVal: new Object()), error);
+  check(create([error],
+      isError: (_) => true, defaultValue: new Object()), error);
 
   error = new Exception();
-  check(create([error], isError: (_) => true, defVal: new Object()), error);
+  check(create([error],
+      isError: (_) => true, defaultValue: new Object()), error);
 
-  check(create<int>([1, 2, 3], isError: (x) => x.isOdd, defVal: 42), 1);
+  check(create<int>([1, 2, 3], isError: (x) => x.isOdd, defaultValue: 42), 1);
 }
diff --git a/LibTest/async/Stream/asBroadcastStream_A04_t03.test.dart b/LibTest/async/Stream/asBroadcastStream_A04_t03.test.dart
index 1f0b10b..f0f290f 100644
--- a/LibTest/async/Stream/asBroadcastStream_A04_t03.test.dart
+++ b/LibTest/async/Stream/asBroadcastStream_A04_t03.test.dart
@@ -79,5 +79,5 @@
     }
   }
 
-  timer = new Timer.periodic(durationMs(10), addSubscribersIfNeeded);
+  timer = Timer.periodic(durationInMilliseconds(10), addSubscribersIfNeeded);
 }
diff --git a/LibTest/async/Stream/asBroadcastStream_A05_t02.test.dart b/LibTest/async/Stream/asBroadcastStream_A05_t02.test.dart
index c54fcc9..fc11030 100644
--- a/LibTest/async/Stream/asBroadcastStream_A05_t02.test.dart
+++ b/LibTest/async/Stream/asBroadcastStream_A05_t02.test.dart
@@ -16,11 +16,13 @@
 import "allTests_A02.lib.dart" as StreamTests;
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream s = create([], isError:(_) => false, defVal: new Object());
+  Stream s = create([], isError:(_) => false, defaultValue: Object());
   if (!s.isBroadcast) {
     StreamTests.test(
-        <T>(Iterable<T> data, {bool isError(T x)?, required T defVal}) {
-          return create<T>(data, isError: isError, defVal: defVal).asBroadcastStream();
+        <T>(Iterable<T> data, { bool isError(T x)?, required T defaultValue }) {
+          return create<T>(data,
+              isError: isError,
+              defaultValue: defaultValue).asBroadcastStream();
         }
     );
   }
diff --git a/LibTest/async/Stream/asyncMap_A01_t04.test.dart b/LibTest/async/Stream/asyncMap_A01_t04.test.dart
index 5902a38..551034b 100644
--- a/LibTest/async/Stream/asyncMap_A01_t04.test.dart
+++ b/LibTest/async/Stream/asyncMap_A01_t04.test.dart
@@ -21,7 +21,8 @@
 void check<T>(Stream<T> stream, List<T> expected) {
   AsyncExpect.data(
       expected,
-      stream.asyncMap((e) => new Future.delayed(durationMs(50), () => e))
+      stream.asyncMap((e) =>
+          new Future.delayed(durationInMilliseconds(50), () => e))
   );
 }
 
diff --git a/LibTest/async/Stream/asyncMap_A03_t01.test.dart b/LibTest/async/Stream/asyncMap_A03_t01.test.dart
index f8d5b47..3eb9c7c 100644
--- a/LibTest/async/Stream/asyncMap_A03_t01.test.dart
+++ b/LibTest/async/Stream/asyncMap_A03_t01.test.dart
@@ -23,9 +23,11 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream stream = create(["a", "b", "c"], isError: (e) => true, defVal: "");
+  Stream stream = create(
+      ["a", "b", "c"], isError: (e) => true, defaultValue: "");
   AsyncExpect.events([], ["a", "b", "c"], stream.asyncMap((e) => e));
 
-  stream = create([1, 2, 3, 4, 5], isError:(e) => e.isEven, defVal: -1);
+  stream = create(
+      [1, 2, 3, 4, 5], isError:(e) => e.isEven, defaultValue: -1);
   AsyncExpect.events([1, 3, 5], [2, 4], stream.asyncMap((e) => e));
 }
diff --git a/LibTest/async/Stream/asyncMap_A03_t03.test.dart b/LibTest/async/Stream/asyncMap_A03_t03.test.dart
index 3495a7b..8a7f18e 100644
--- a/LibTest/async/Stream/asyncMap_A03_t03.test.dart
+++ b/LibTest/async/Stream/asyncMap_A03_t03.test.dart
@@ -14,8 +14,8 @@
 /// ...
 /// Error and done events are passed through unchanged to the returned stream.
 ///
-/// @description Checks that if future returned by [convert] completes
-/// with an error, then this error is passed to returned stream.
+/// @description Checks that if future returned by [convert] completes with an
+/// error, then this error is passed to returned stream.
 /// @author a.semenov@unipro.ru
 
 library asyncMap_A03_t03;
@@ -24,14 +24,16 @@
 
 void test(CreateStreamFunction create) {
   Stream<String> stream1 = create(["a", "b", "c"]);
-  AsyncExpect.events([], ["a", "b", "c"], stream1.asyncMap((e) => new Future.error(e)));
+  AsyncExpect.events([],
+      ["a", "b", "c"], stream1.asyncMap((e) => new Future.error(e)));
 
   Stream<int> stream2 = create([1, 2, 3, 4, 5]);
   AsyncExpect.events(
     [1, 3, 5],
     [2, 4],
     stream2.asyncMap(
-      (int e) => new Future.delayed(durationMs(50), () => e.isOdd ? e : throw e)
+      (int e) => new Future.delayed(
+          durationInMilliseconds(50), () => e.isOdd ? e : throw e)
     )
   );
 }
diff --git a/LibTest/async/Stream/contains_A03_t01.test.dart b/LibTest/async/Stream/contains_A03_t01.test.dart
index 43072fe..81f58a3 100644
--- a/LibTest/async/Stream/contains_A03_t01.test.dart
+++ b/LibTest/async/Stream/contains_A03_t01.test.dart
@@ -14,6 +14,6 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   Error error = new Error();
-  Stream s = create([error], isError: (e) => true, defVal: new Object());
+  Stream s = create([error], isError: (e) => true, defaultValue: new Object());
   AsyncExpect.error(error, s.contains(1));
 }
diff --git a/LibTest/async/Stream/contains_A03_t02.test.dart b/LibTest/async/Stream/contains_A03_t02.test.dart
index ac8ff55..c192bbe 100644
--- a/LibTest/async/Stream/contains_A03_t02.test.dart
+++ b/LibTest/async/Stream/contains_A03_t02.test.dart
@@ -14,6 +14,7 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   Error error = new Error();
-  Stream s = create([1, error], isError: (e) => e is Error, defVal: new Object());
+  Stream s = create(
+      [1, error], isError: (e) => e is Error, defaultValue: Object());
   AsyncExpect.value(true, s.contains(1));
 }
diff --git a/LibTest/async/Stream/contains_A03_t03.test.dart b/LibTest/async/Stream/contains_A03_t03.test.dart
index 9e84624..791ccfe 100644
--- a/LibTest/async/Stream/contains_A03_t03.test.dart
+++ b/LibTest/async/Stream/contains_A03_t03.test.dart
@@ -14,6 +14,7 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   Error error = new Error();
-  Stream s = create([1, 2, error, 3, 4], isError: (e) => e is Error, defVal: new Object());
+  Stream s = create(
+      [1, 2, error, 3, 4], isError: (e) => e is Error, defaultValue: Object());
   AsyncExpect.error(error, s.contains(4));
 }
diff --git a/LibTest/async/Stream/distinct_A04_t01.test.dart b/LibTest/async/Stream/distinct_A04_t01.test.dart
index 4e83c4c..beec758 100644
--- a/LibTest/async/Stream/distinct_A04_t01.test.dart
+++ b/LibTest/async/Stream/distinct_A04_t01.test.dart
@@ -3,12 +3,12 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// @assertion Stream<T> distinct([bool equals(T previous, T next)])
-///    Skips data events if they are equal to the previous data event.
-///    The returned stream provides the same events as this stream, except that it
+/// Skips data events if they are equal to the previous data event.
+/// The returned stream provides the same events as this stream, except that it
 /// never provides two consecutive data events that are equal.
-/// @description Checks that errors in original stream are copied to the returned
-/// stream. [equals] is omitted.
-/// @issue #29627
+/// @description Checks that errors in original stream are copied to the
+/// returned stream. [equals] is omitted.
+/// @issue 29627
 /// @author a.semenov@unipro.ru
 
 library distinct_A04_t01;
@@ -21,12 +21,16 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 0), [], []);
-  check<int>(create([1, 2, 2, 3], isError: (e) => e.isEven, defVal: 42), [1, 3], [2, 2]);
+  check(create([], defaultValue: 0), [], []);
+  check<int>(create([1, 2, 2, 3], isError: (e) => e.isEven, defaultValue: 42),
+      [1, 3], [2, 2]);
   check<int>(
-      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isEven, defVal: 42), [1, 3], [2, 2]);
+      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isEven, defaultValue: 42),
+      [1, 3], [2, 2]);
   check<int>(
-      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isOdd, defVal: 42), [2], [1, 1, 3, 3]);
+      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isOdd, defaultValue: 42),
+      [2], [1, 1, 3, 3]);
   check<int?>(
-      create([1, 2, null, null], isError: (e) => e is num, defVal: 42), [null], [1, 2]);
+      create([1, 2, null, null], isError: (e) => e is num, defaultValue: 42),
+      [null], [1, 2]);
 }
diff --git a/LibTest/async/Stream/distinct_A04_t02.test.dart b/LibTest/async/Stream/distinct_A04_t02.test.dart
index b27e42c..dcb8404 100644
--- a/LibTest/async/Stream/distinct_A04_t02.test.dart
+++ b/LibTest/async/Stream/distinct_A04_t02.test.dart
@@ -22,12 +22,16 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 0), [], []);
-  check<int>(create([1, 2, 2, 3], isError: (e) => e.isEven, defVal: 42), [1, 3], [2, 2]);
+  check(create([], defaultValue: 0), [], []);
+  check<int>(create([1, 2, 2, 3], isError: (e) => e.isEven, defaultValue: 42),
+      [1, 3], [2, 2]);
   check<int>(
-      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isEven, defVal: 42), [1, 3], [2, 2]);
+      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isEven, defaultValue: 42),
+      [1, 3], [2, 2]);
   check<int>(
-      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isOdd, defVal: 42), [2], [1, 1, 3, 3]);
+      create([1, 1, 2, 2, 3, 3], isError: (e) => e.isOdd, defaultValue: 42),
+      [2], [1, 1, 3, 3]);
   check<int?>(
-      create([1, 2, null, null], isError: (e) => e is num, defVal: 42), [null], [1, 2]);
+      create([1, 2, null, null], isError: (e) => e is num, defaultValue: 42),
+      [null], [1, 2]);
 }
diff --git a/LibTest/async/Stream/drain_A01_t01.test.dart b/LibTest/async/Stream/drain_A01_t01.test.dart
index b453468..f4c4e0c 100644
--- a/LibTest/async/Stream/drain_A01_t01.test.dart
+++ b/LibTest/async/Stream/drain_A01_t01.test.dart
@@ -3,13 +3,13 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// @assertion Future drain([futureValue])
-///    Discards all data on the stream, but signals when it's done or an error
+/// Discards all data on the stream, but signals when it's done or an error
 /// occurred.
-///    When subscribing using drain, cancelOnError will be true.
+/// When subscribing using drain, cancelOnError will be true.
 /// This means that the future will complete with the first error on the stream
 /// and then cancel the subscription.
-/// @description Checks that the future will complete with the first error
-/// on the stream.
+/// @description Checks that the future will complete with the first error on
+/// the stream.
 /// @author kaigorodov
 
 library drain_A01_t01;
@@ -18,6 +18,7 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream<int> s = create([1, 2, 3, 4, 5], isError: (e) => true, defVal: 42);
+  Stream<int> s = create([1, 2, 3, 4, 5], isError: (e) => true,
+      defaultValue: 42);
   AsyncExpect.error(1, s.drain());
 }
diff --git a/LibTest/async/Stream/elementAt_A02_t01.test.dart b/LibTest/async/Stream/elementAt_A02_t01.test.dart
index b5245e1..ee444f6 100644
--- a/LibTest/async/Stream/elementAt_A02_t01.test.dart
+++ b/LibTest/async/Stream/elementAt_A02_t01.test.dart
@@ -17,7 +17,7 @@
 void test(CreateStreamWithErrorsFunction create) {
   for (int k = 0; k < 10; k++) {
     Iterable<int> i = new Iterable<int>.generate(10, (int x) => x);
-    Stream<int> s = create(i, isError: (e) => e == k, defVal: 42);
+    Stream<int> s = create(i, isError: (e) => e == k, defaultValue: 42);
     AsyncExpect.error(k, s.elementAt(k));
   }
 }
diff --git a/LibTest/async/Stream/every_A02_t01.test.dart b/LibTest/async/Stream/every_A02_t01.test.dart
index 1a65e26..74da912 100644
--- a/LibTest/async/Stream/every_A02_t01.test.dart
+++ b/LibTest/async/Stream/every_A02_t01.test.dart
@@ -19,15 +19,11 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   Object error = new ArgumentError(1);
-  check(create([error], isError: (e) => true, defVal: new Object()), error);
-  check(
-      create([1, 2, error, 3, 4],
-          isError: (e) => e is ArgumentError, defVal: new Object()),
-      error);
+  check(create([error], isError: (e) => true, defaultValue: Object()), error);
+  check(create([1, 2, error, 3, 4], isError: (e) => e is ArgumentError,
+      defaultValue: Object()), error);
   error = new StateError("");
-  check(create([error], isError: (e) => true, defVal: new Object()), error);
-  check(
-      create([1, 2, error, 3, 4],
-          isError: (e) => e is StateError, defVal: new Object()),
-      error);
+  check(create([error], isError: (e) => true, defaultValue: Object()), error);
+  check(create([1, 2, error, 3, 4], isError: (e) => e is StateError,
+      defaultValue: Object()), error);
 }
diff --git a/LibTest/async/Stream/firstWhere_A03_t01.test.dart b/LibTest/async/Stream/firstWhere_A03_t01.test.dart
index fea52ba..329d9c7 100644
--- a/LibTest/async/Stream/firstWhere_A03_t01.test.dart
+++ b/LibTest/async/Stream/firstWhere_A03_t01.test.dart
@@ -7,15 +7,15 @@
 ///
 /// Finds the first element of this stream matching test.
 ///
-/// Returns a future that is completed with the first element of this stream that
-/// test returns true for.
+/// Returns a future that is completed with the first element of this stream
+/// that test returns true for.
 ///
-/// If no such element is found before this stream is done, and a orElse function
-/// is provided, the result of calling orElse becomes the value of the future. If
-/// orElse throws, the returned future is completed with that error.
+/// If no such element is found before this stream is done, and a orElse
+/// function is provided, the result of calling orElse becomes the value of the
+/// future. If orElse throws, the returned future is completed with that error.
 ///
-/// If this stream emits an error before the first matching element, the returned
-/// future is completed with that error, and processing stops.
+/// If this stream emits an error before the first matching element, the
+/// returned future is completed with that error, and processing stops.
 ///
 /// Stops listening to the stream after the first matching element or error has
 /// been received.
@@ -38,6 +38,6 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream s = create([1, 2, 3, 4, 5], isError: (x) => x == 4, defVal: 42);
+  Stream s = create([1, 2, 3, 4, 5], isError: (x) => x == 4, defaultValue: 42);
   AsyncExpect.error(4, s.firstWhere((v) => v == 5));
 }
diff --git a/LibTest/async/Stream/first_A03_t01.test.dart b/LibTest/async/Stream/first_A03_t01.test.dart
index 65c27c4..2aac7c8 100644
--- a/LibTest/async/Stream/first_A03_t01.test.dart
+++ b/LibTest/async/Stream/first_A03_t01.test.dart
@@ -3,10 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// @assertion Future<T> first
-/// If an error event occurs before the first data event, the resulting
-/// future is completed with that error.
-/// @description Checks that if error event occurs before the first data
-/// event, the future completes with that error.
+/// If an error event occurs before the first data event, the resulting future
+/// is completed with that error.
+/// @description Checks that if error event occurs before the first data event,
+/// the future completes with that error.
 /// @author ilya
 
 library first_A03_t01;
@@ -15,6 +15,6 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream s = create([1, 2, 3], isError: (_) => true, defVal: 42);
+  Stream s = create([1, 2, 3], isError: (_) => true, defaultValue: 42);
   AsyncExpect.error(1, s.first);
 }
diff --git a/LibTest/async/Stream/forEach_A02_t01.test.dart b/LibTest/async/Stream/forEach_A02_t01.test.dart
index 44c4187..e04f400 100644
--- a/LibTest/async/Stream/forEach_A02_t01.test.dart
+++ b/LibTest/async/Stream/forEach_A02_t01.test.dart
@@ -5,8 +5,8 @@
 /// @assertion Future forEach(void action(T element))
 /// Completes the future with an error if the stream has an error event, or if
 /// action throws.
-/// @description Checks that the future is completed with error if the stream has
-/// an error event.
+/// @description Checks that the future is completed with error if the stream
+/// has an error event.
 /// @author kaigorodov
 
 library forEach_A02_t01;
@@ -19,12 +19,14 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3, 4], isError: (v) => v == 4, defVal: 42), 4);
+  check(create([1, 2, 3, 4], isError: (v) => v == 4, defaultValue: 42), 4);
   List list = [];
   check(
-      create([null, "2", -3, 4.0, list], isError: (v) => v == list, defVal: 42),
+      create([null, "2", -3, 4.0, list], isError: (v) => v == list,
+          defaultValue: 42),
       list);
   check(
-      create([null, "2", -3, 4.0, list], isError: (v) => v == 4.0, defVal: 42),
+      create([null, "2", -3, 4.0, list], isError: (v) => v == 4.0,
+          defaultValue: 42),
       4.0);
 }
diff --git a/LibTest/async/Stream/handleError_A01_t01.test.dart b/LibTest/async/Stream/handleError_A01_t01.test.dart
index 5ae4d26..53aa23c 100644
--- a/LibTest/async/Stream/handleError_A01_t01.test.dart
+++ b/LibTest/async/Stream/handleError_A01_t01.test.dart
@@ -6,7 +6,8 @@
 /// Creates a wrapper Stream that intercepts some errors from this stream.
 /// If this stream sends an error that matches test, then it is intercepted by
 /// the onError function.
-/// An asynchronous error e is matched by a test function if test(e) returns true.
+/// An asynchronous error e is matched by a test function if test(e) returns
+/// true.
 /// @description Checks that an error e intercepted by [onError] function
 /// if test(e) returns true.
 /// @author a.semenov@unipro.ru
@@ -36,14 +37,15 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 42), (x) => true, [], [], []);
-  check(create([], isError: (x) => true, defVal: 42), (x) => true, [], [], []);
-  check(create([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42),
+  check(create([], defaultValue: 42), (x) => true, [], [], []);
+  check(create([], isError: (x) => true, defaultValue: 42),
+          (x) => true, [], [], []);
+  check(create([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42),
       (x) => x.isEven, [], [2, 4], [1, 3, 5]);
 
   check(
       create(["a", 1, "b", 2, "c", 3, "d", 4, "e", 5, "f"],
-          isError: (x) => x is int, defVal: 42),
+          isError: (x) => x is int, defaultValue: 42),
       (x) => (x is int && x.isEven), // test function
       ["a", "b", "c", "d", "e", "f"], // expected data
       [2, 4], // intercepted errors
diff --git a/LibTest/async/Stream/handleError_A02_t01.test.dart b/LibTest/async/Stream/handleError_A02_t01.test.dart
index 6cced50..fa8c0e4 100644
--- a/LibTest/async/Stream/handleError_A02_t01.test.dart
+++ b/LibTest/async/Stream/handleError_A02_t01.test.dart
@@ -30,14 +30,14 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 42), [], []);
-  check(create([], isError: (x) => true, defVal: 42), [], []);
+  check(create([], defaultValue: 42), [], []);
+  check(create([], isError: (x) => true, defaultValue: 42), [], []);
 
-  check(create([1, 2, 3, 4], defVal: 42), [1, 2, 3, 4], []);
-  check(
-      create([1, 2, 3, 4], isError: (x) => true, defVal: 42), [], [1, 2, 3, 4]);
-  check(create([1, 2, 3, 4], isError: (x) => x.isEven, defVal: 42), [1, 3],
-      [2, 4]);
-  check(create([null, "2", -3, 4.0, []], isError: (x) => x is num, defVal: 42),
-      [null, "2", []], [-3, 4.0]);
+  check(create([1, 2, 3, 4], defaultValue: 42), [1, 2, 3, 4], []);
+  check(create([1, 2, 3, 4], isError: (x) => true, defaultValue: 42),
+      [], [1, 2, 3, 4]);
+  check(create([1, 2, 3, 4], isError: (x) => x.isEven, defaultValue: 42),
+      [1, 3], [2, 4]);
+  check(create([null, "2", -3, 4.0, []], isError: (x) => x is num,
+      defaultValue: 42), [null, "2", []], [-3, 4.0]);
 }
diff --git a/LibTest/async/Stream/handleError_A03_t01.test.dart b/LibTest/async/Stream/handleError_A03_t01.test.dart
index 5c47211..d60fcbc 100644
--- a/LibTest/async/Stream/handleError_A03_t01.test.dart
+++ b/LibTest/async/Stream/handleError_A03_t01.test.dart
@@ -14,7 +14,8 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-void check(Stream s, void onError(error), List data, List intercepted, List expected) {
+void check(
+    Stream s, void onError(error), List data, List intercepted, List expected) {
   List actualIntercepted = [];
   List actualErrors = [];
   List actualData = [];
@@ -41,28 +42,23 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 42), (e) => throw e, [], [], []);
-  check(create([], isError:(x) => true, defVal: 42), (e) => throw e, [], [], []);
+  check(create([], defaultValue: 42), (e) => throw e, [], [], []);
+  check(create([], isError:(x) => true, defaultValue: 42),
+          (e) => throw e, [], [], []);
 
-  check(create([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42),
+  check(create([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42),
       (x) => throw x, [], [1, 2, 3, 4, 5], [1, 2, 3, 4, 5]);
 
-  check(
-      create(
-          ["a", 1, "b", 2, "c", 3, "d", 4, "e", 5, "f"],
-          isError: (x) => x is num, defVal: 42
-      ),
+  check(create(["a", 1, "b", 2, "c", 3, "d", 4, "e", 5, "f"],
+      isError: (x) => x is num, defaultValue: 42),
       (x) { if (x.isEven) { throw x; }}, // onError function
       ["a", "b", "c", "d", "e", "f"], // expected data
       [1, 2, 3, 4, 5],  // intercepted errors
       [2,4] // rethrown errors
   );
 
-  check(
-      create(
-          ["a", 1, "b", 2, "c", 3, "d", 4, "e", 5, "f"],
-          isError: (x) => x is num, defVal: 42
-      ),
+  check(create(["a", 1, "b", 2, "c", 3, "d", 4, "e", 5, "f"],
+          isError: (x) => x is num, defaultValue: 42),
       (x) { if (x.isEven) { throw x + 10; }}, // onError function
       ["a", "b", "c", "d", "e", "f"], // expected data
       [1, 2, 3, 4, 5],  // intercepted errors
diff --git a/LibTest/async/Stream/handleError_A05_t01.test.dart b/LibTest/async/Stream/handleError_A05_t01.test.dart
index d1226e6..5339799 100644
--- a/LibTest/async/Stream/handleError_A05_t01.test.dart
+++ b/LibTest/async/Stream/handleError_A05_t01.test.dart
@@ -21,7 +21,7 @@
   List errors = [];
   List traces = [];
   asyncStart();
-  Stream s = create([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42);
+  Stream s = create([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42);
   s.handleError((error, stackTrace) {
     errors.add(error);
     traces.add(stackTrace);
diff --git a/LibTest/async/Stream/handleError_A07_t01.test.dart b/LibTest/async/Stream/handleError_A07_t01.test.dart
index 8e68646..27f110a 100644
--- a/LibTest/async/Stream/handleError_A07_t01.test.dart
+++ b/LibTest/async/Stream/handleError_A07_t01.test.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// @assertion Stream<T> handleError(Function onError, {bool test(error)})
-///    If a broadcast stream is listened to more than once, each subscription will
+/// If a broadcast stream is listened to more than once, each subscription will
 /// individually perform the test and handle the error.
 /// @description Checks that [test] and [onError] are called once per listener
 /// per error.
@@ -15,8 +15,8 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream s =
-      create(["a", 1, "b", 2, "c", 3], isError: (x) => x is num, defVal: 42);
+  Stream s = create(["a", 1, "b", 2, "c", 3], isError: (x) => x is num,
+      defaultValue: 42);
   Map onErrorCalls = new Map();
   Map testCalls = new Map();
   asyncStart();
diff --git a/LibTest/async/Stream/isEmpty_A03_t01.test.dart b/LibTest/async/Stream/isEmpty_A03_t01.test.dart
index cc65592..6886069 100644
--- a/LibTest/async/Stream/isEmpty_A03_t01.test.dart
+++ b/LibTest/async/Stream/isEmpty_A03_t01.test.dart
@@ -7,14 +7,16 @@
 /// error.
 /// @description Checks that returned future is completed with the first error,
 /// that appears in the stream
-/// @issue #29730
+/// @issue 29730
 /// @author a.semenov@unipro.ru
 
 library isEmpty_A03_t01;
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  AsyncExpect.value(true, create([], defVal: 42).isEmpty);
-  AsyncExpect.error(1, create([1, 2, 3, null], isError:(x) => x==1, defVal: 42).isEmpty);
-  AsyncExpect.value(false, create([1, 2, 3, null], isError:(x) => x==3, defVal: 42).isEmpty);
+  AsyncExpect.value(true, create([], defaultValue: 42).isEmpty);
+  AsyncExpect.error(1,
+      create([1, 2, 3, null], isError:(x) => x==1, defaultValue: 42).isEmpty);
+  AsyncExpect.value(false,
+      create([1, 2, 3, null], isError:(x) => x==3, defaultValue: 42).isEmpty);
 }
diff --git a/LibTest/async/Stream/join_A02_t01.test.dart b/LibTest/async/Stream/join_A02_t01.test.dart
index d73abab..1973da8 100644
--- a/LibTest/async/Stream/join_A02_t01.test.dart
+++ b/LibTest/async/Stream/join_A02_t01.test.dart
@@ -16,7 +16,8 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   Error error = new Error();
-  Stream s = create([1, 2, error, 4, 5], isError: (e) => e is Error, defVal: 42);
+  Stream s = create([1, 2, error, 4, 5], isError: (e) => e is Error,
+      defaultValue: 42);
 
   AsyncExpect.error(error, s.join());
 }
diff --git a/LibTest/async/Stream/lastWhere_A01_t02.test.dart b/LibTest/async/Stream/lastWhere_A01_t02.test.dart
index da767a1..a877839 100644
--- a/LibTest/async/Stream/lastWhere_A01_t02.test.dart
+++ b/LibTest/async/Stream/lastWhere_A01_t02.test.dart
@@ -26,7 +26,10 @@
 void check<T>(Stream<T> s, bool test(T element), T expected) {
   bool orElseCalled = false;
   asyncStart();
-  s.lastWhere(test, orElse:() {orElseCalled = true;})
+  s.lastWhere(test, orElse:() {
+    orElseCalled = true;
+    return null as T;
+  })
    .then((T actual){
      Expect.equals(expected, actual);
      Expect.isFalse(orElseCalled);
@@ -36,8 +39,8 @@
 
 void test(CreateStreamFunction create) {
   check(create<int>([1, 2, 3]), (int element) => true, 3);
-  check(create<int>([1, 2, 3]), (int element) => element != null, 3);
-  check(create<int>([1, 2, 3, null]), (int element) => element == null, null);
+  check(create<int?>([1, 2, 3]), (int? element) => element != null, 3);
+  check(create<int?>([1, 2, 3, null]), (int? element) => element == null, null);
   check(create<int>([1, 2, 3]), (int element) => element > 0, 3);
   check(create<int>(new Iterable<int>.generate(10, (int index) => index * 5)),
       (int element) => element != 30, 45);
diff --git a/LibTest/async/Stream/lastWhere_A03_t01.test.dart b/LibTest/async/Stream/lastWhere_A03_t01.test.dart
index 65b274d..bbb3e93 100644
--- a/LibTest/async/Stream/lastWhere_A03_t01.test.dart
+++ b/LibTest/async/Stream/lastWhere_A03_t01.test.dart
@@ -30,10 +30,10 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check<int>(
-      create([1, 2, 3], isError: (e) => true, defVal: 42), (x) => x > 0, 1);
-  check<int>(
-      create([1, 2, 3], isError: (e) => e == 3, defVal: 42), (x) => x > 0, 3);
-  check<int>(create([-1, 1, -2, 2, 3], isError: (e) => e == 3, defVal: 42),
+  check<int>(create([1, 2, 3], isError: (e) => true, defaultValue: 42),
+          (x) => x > 0, 1);
+  check<int>(create([1, 2, 3], isError: (e) => e == 3, defaultValue: 42),
+          (x) => x > 0, 3);
+  check<int>(create([-1, 1, -2, 2, 3], isError: (e) => e == 3, defaultValue: 42),
       (x) => x < 0, 3);
 }
diff --git a/LibTest/async/Stream/last_A03_t01.test.dart b/LibTest/async/Stream/last_A03_t01.test.dart
index 808dc7f..53c0adf 100644
--- a/LibTest/async/Stream/last_A03_t01.test.dart
+++ b/LibTest/async/Stream/last_A03_t01.test.dart
@@ -5,8 +5,8 @@
 /// @assertion Future<T> last
 /// If an error event occurs before the first data event, the resulting future
 /// is completed with that error.
-/// @description Checks that if error event occurs before the first data
-/// event, the future completes with that error.
+/// @description Checks that if error event occurs before the first data event,
+/// the future completes with that error.
 /// @author ilya
 /// @author a.semenov@unipro.ru
 
@@ -17,14 +17,12 @@
   Error error = new Error();
   AsyncExpect.error(
     error,
-    create([1, 2, error, 4, 5], isError: (e) => e is Error, defVal: 42).last
-  );
+    create(
+        [1, 2, error, 4, 5], isError: (e) => e is Error, defaultValue: 42).last);
   AsyncExpect.error(
       error,
-      create([error, 4, 5], isError: (e) => e is Error, defVal: 42).last
-  );
+      create([error, 4, 5], isError: (e) => e is Error, defaultValue: 42).last);
   AsyncExpect.error(
       error,
-      create([1, 2, error], isError: (e) => e is Error, defVal: 42).last
-  );
+      create([1, 2, error], isError: (e) => e is Error, defaultValue: 42).last);
 }
diff --git a/LibTest/async/Stream/length_A02_t01.test.dart b/LibTest/async/Stream/length_A02_t01.test.dart
index 1f6931c..3612715 100644
--- a/LibTest/async/Stream/length_A02_t01.test.dart
+++ b/LibTest/async/Stream/length_A02_t01.test.dart
@@ -3,8 +3,8 @@
 // BSD-style license that can be found in the LICENSE file.
 
 /// @assertion Future<int> length
-///    If the stream contains an error, the returned future is completed with
-/// that error, and processing stops.
+/// If the stream contains an error, the returned future is completed with that
+/// error, and processing stops.
 /// @description Checks that If the stream contains an error, the returned
 /// future is completed with that error, and processing stops
 /// @author a.semenov@unipro.ru
@@ -14,11 +14,11 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  AsyncExpect.error(1, create([1], isError: (_) => true, defVal: 42).length);
   AsyncExpect.error(
-      3, create([1, 2, 3, null], isError: (e) => e == 3, defVal: 42).length);
-  AsyncExpect.error(
-      12,
+      1, create([1], isError: (_) => true, defaultValue: 42).length);
+  AsyncExpect.error(3,
+      create([1, 2, 3, null], isError: (e) => e == 3, defaultValue: 42).length);
+  AsyncExpect.error(12,
       create<int>(new Iterable.generate(10, (int i) => i * 2),
-          isError: (e) => e > 10, defVal: 42).length);
+          isError: (e) => e > 10, defaultValue: 42).length);
 }
diff --git a/LibTest/async/Stream/listen_A03_t01.test.dart b/LibTest/async/Stream/listen_A03_t01.test.dart
index 8f10fc7..a5781a2 100644
--- a/LibTest/async/Stream/listen_A03_t01.test.dart
+++ b/LibTest/async/Stream/listen_A03_t01.test.dart
@@ -6,8 +6,8 @@
 ///   {Function onError, void onDone(), bool cancelOnError})
 /// On errors from this stream, the onError handler is given a object describing
 /// the error.
-/// @description Checks that the onError handler is given an object describing the
-/// error.
+/// @description Checks that the onError handler is given an object describing
+/// the error.
 /// @author kaigorodov
 
 library listen_A03_t01;
@@ -31,13 +31,14 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 42), [], []);
-  check(create([1, 2, 3, 4], isError: (x) => false, defVal: 42), [1, 2, 3, 4],
-      []);
-  check(
-      create([1, 2, 3, 4], isError: (x) => true, defVal: 42), [], [1, 2, 3, 4]);
-  check<int>(create([1, 2, 3, 4], isError: (x) => x.isOdd, defVal: 42), [2, 4],
-      [1, 3]);
-  check(create([null, "2", -3, 4.0, []], isError: (x) => x is num, defVal: 42),
+  check(create([], defaultValue: 42), [], []);
+  check(create([1, 2, 3, 4], isError: (x) => false, defaultValue: 42),
+      [1, 2, 3, 4], []);
+  check(create([1, 2, 3, 4], isError: (x) => true, defaultValue: 42),
+      [], [1, 2, 3, 4]);
+  check<int>(create([1, 2, 3, 4], isError: (x) => x.isOdd, defaultValue: 42),
+      [2, 4], [1, 3]);
+  check(create(
+        [null, "2", -3, 4.0, []], isError: (x) => x is num, defaultValue: 42),
       [null, "2", []], [-3, 4.0]);
 }
diff --git a/LibTest/async/Stream/listen_A04_t01.test.dart b/LibTest/async/Stream/listen_A04_t01.test.dart
index 8770241..c539c3c 100644
--- a/LibTest/async/Stream/listen_A04_t01.test.dart
+++ b/LibTest/async/Stream/listen_A04_t01.test.dart
@@ -8,7 +8,7 @@
 /// reported. The default is false.
 /// @description Checks that if cancelOnError is true, the subscription is ended
 /// when the first error is reported.
-/// @issue #25967
+/// @issue 25967
 /// @author kaigorodov
 /// @author a.semenov@unipro.ru
 
@@ -27,7 +27,7 @@
       onError: (Object error) {
         errorSink.add(error);
         // wait for possible additional error
-        new Future.delayed(durationMs(500), (){
+        new Future.delayed(durationInMilliseconds(500), (){
           Expect.listEquals(data, dataSink);
           Expect.listEquals(errors, errorSink);
           asyncEnd();
@@ -44,14 +44,15 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([], defVal: 42), [], []);
-  check(create([1, 2, 3, 4], isError:(x) => false, defVal: 42), [1, 2, 3, 4], []);
-  check(create([1, 2, 3, 4], isError:(x) => true, defVal: 42), [], [1]);
-  check<int>(create([1, 2, 3, 4], isError:(x) => x.isOdd, defVal: 42), [], [1]);
-  check<int>(create([1, 2, 3, 4], isError:(x) => x.isEven, defVal: 42), [1], [2]);
-  check(
-      create([null, "2", -3, 4.0, []], isError:(x) => x is num, defVal: 42),
-      [null, "2"],
-      [-3]
-  );
+  check(create([], defaultValue: 42), [], []);
+  check(create([1, 2, 3, 4], isError:(x) => false, defaultValue: 42),
+      [1, 2, 3, 4], []);
+  check(create([1, 2, 3, 4], isError:(x) => true, defaultValue: 42), [], [1]);
+  check<int>(create([1, 2, 3, 4], isError:(x) => x.isOdd, defaultValue: 42),
+      [], [1]);
+  check<int>(create([1, 2, 3, 4], isError:(x) => x.isEven, defaultValue: 42),
+      [1], [2]);
+  check(create(
+        [null, "2", -3, 4.0, []], isError:(x) => x is num, defaultValue: 42),
+      [null, "2"], [-3]);
 }
diff --git a/LibTest/async/Stream/map_A03_t01.test.dart b/LibTest/async/Stream/map_A03_t01.test.dart
index 2950fa0..112e576 100644
--- a/LibTest/async/Stream/map_A03_t01.test.dart
+++ b/LibTest/async/Stream/map_A03_t01.test.dart
@@ -4,7 +4,6 @@
 
 /// @assertion Stream<S> map<S>(S convert(T event))
 /// Error and done events are passed through unchanged to the returned stream.
-///
 /// @description Checks that each error of this stream is passed to returned
 /// stream.
 /// @author a.semenov@unipro.ru
@@ -14,9 +13,9 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  Stream stream = create(["a", "b", "c"], isError:(e) => true, defVal: "");
+  Stream stream = create(["a", "b", "c"], isError:(e) => true, defaultValue: "");
   AsyncExpect.events([], ["a", "b", "c"], stream.map((e) => e));
 
-  stream = create([1, 2, 3, 4, 5], isError:(e) => e.isEven, defVal: 42);
+  stream = create([1, 2, 3, 4, 5], isError:(e) => e.isEven, defaultValue: 42);
   AsyncExpect.events([1, 3, 5], [2, 4], stream.map((e) => e));
 }
diff --git a/LibTest/async/Stream/pipe_A01_t02.test.dart b/LibTest/async/Stream/pipe_A01_t02.test.dart
index df1949b..6508516 100644
--- a/LibTest/async/Stream/pipe_A01_t02.test.dart
+++ b/LibTest/async/Stream/pipe_A01_t02.test.dart
@@ -41,7 +41,8 @@
     }
   );
 
-  Stream<int> s = create([1, 2, 3, 4, 5], isError:(x) => x.isEven, defVal: 42);
+  Stream<int> s =
+      create([1, 2, 3, 4, 5], isError:(x) => x.isEven, defaultValue: 42);
 
   asyncStart();
   s.pipe(c).then((x) {
diff --git a/LibTest/async/Stream/reduce_A03_t01.test.dart b/LibTest/async/Stream/reduce_A03_t01.test.dart
index e522607..8693ddc 100644
--- a/LibTest/async/Stream/reduce_A03_t01.test.dart
+++ b/LibTest/async/Stream/reduce_A03_t01.test.dart
@@ -18,10 +18,10 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3, 4, 5], isError: (_) => true, defVal: 42),
+  check(create([1, 2, 3, 4, 5], isError: (_) => true, defaultValue: 42),
       (int p, int e) => p + e, 1);
-  check<int>(create([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check<int>(create([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (int p, int e) => p * e, 2);
-  check(create([1, 2, 3, 4, 5], isError: (x) => x == 5, defVal: 42),
+  check(create([1, 2, 3, 4, 5], isError: (x) => x == 5, defaultValue: 42),
       (int p, int e) => p + e, 5);
 }
diff --git a/LibTest/async/Stream/single_A03_t01.test.dart b/LibTest/async/Stream/single_A03_t01.test.dart
index 689a9d2..5055fde 100644
--- a/LibTest/async/Stream/single_A03_t01.test.dart
+++ b/LibTest/async/Stream/single_A03_t01.test.dart
@@ -15,8 +15,12 @@
 import "../../../Utils/expect.dart";
 
 void test(CreateStreamWithErrorsFunction create) {
-  AsyncExpect.error(1, create([1, 2, 3], isError: (_) => true, defVal: 42).single);
-  AsyncExpect.error(1, create([1, 2, 3], isError: (x) => x == 1, defVal: 42).single);
-  AsyncExpect.error(2, create([1, 2], isError: (x) => x == 2, defVal: 42).single);
-  AsyncExpect.error(2, create([1, 2, 3], isError: (x) => x == 2, defVal: 42).single);
+  AsyncExpect.error(
+      1, create([1, 2, 3], isError: (_) => true, defaultValue: 42).single);
+  AsyncExpect.error(
+      1, create([1, 2, 3], isError: (x) => x == 1, defaultValue: 42).single);
+  AsyncExpect.error(
+      2, create([1, 2], isError: (x) => x == 2, defaultValue: 42).single);
+  AsyncExpect.error(
+      2, create([1, 2, 3], isError: (x) => x == 2, defaultValue: 42).single);
 }
diff --git a/LibTest/async/Stream/skipWhile_A02_t01.test.dart b/LibTest/async/Stream/skipWhile_A02_t01.test.dart
index 937784f..f565343 100644
--- a/LibTest/async/Stream/skipWhile_A02_t01.test.dart
+++ b/LibTest/async/Stream/skipWhile_A02_t01.test.dart
@@ -22,14 +22,15 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3], isError: (_) => true, defVal: 42), (_) => false, [],
-      [1, 2, 3]);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42),
-      (x) => x < 4, [4], [1, 3, 5]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42),
+  check(create([1, 2, 3], isError: (_) => true, defaultValue: 42), (_) => false,
+      [], [1, 2, 3]);
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
+          (x) => x < 4, [4], [1, 3, 5]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
       (x) => x == 1, [2, 4], [1, 3, 5]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (x) => x == 1, [3, 5], [2, 4]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 5, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 5, defaultValue: 42),
       (x) => x == 5, [], [1, 2, 3, 4]);
 }
diff --git a/LibTest/async/Stream/skip_A03_t01.test.dart b/LibTest/async/Stream/skip_A03_t01.test.dart
index 04a6752..56e3b82 100644
--- a/LibTest/async/Stream/skip_A03_t01.test.dart
+++ b/LibTest/async/Stream/skip_A03_t01.test.dart
@@ -8,8 +8,8 @@
 /// if listened to at the same time, except that the first [count]
 /// data events are not emitted.
 /// The returned stream is done when this stream is.
-///    If this stream emits fewer than [count] data events
-/// before being done, the returned stream emits no data events.
+/// If this stream emits fewer than [count] data events before being done, the
+/// returned stream emits no data events.
 /// @description Checks that errors in the input stream are propagated to the
 /// returned stream.
 /// @author a.semenov@unipro.ru
@@ -20,25 +20,19 @@
 
 void test(CreateStreamWithErrorsFunction create) {
   AsyncExpect.events([], [1, 2, 3],
-      create([1, 2, 3], isError: (_) => true, defVal: 42).skip(0));
+      create([1, 2, 3], isError: (_) => true, defaultValue: 42).skip(0));
   AsyncExpect.events([], [1, 2, 3],
-      create([1, 2, 3], isError: (_) => true, defVal: 42).skip(1));
+      create([1, 2, 3], isError: (_) => true, defaultValue: 42).skip(1));
   AsyncExpect.events([], [1, 2, 3],
-      create([1, 2, 3], isError: (_) => true, defVal: 42).skip(10));
+      create([1, 2, 3], isError: (_) => true, defaultValue: 42).skip(10));
 
-  AsyncExpect.events(
-      [],
-      [1, 3, 5],
-      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42)
+  AsyncExpect.events([], [1, 3, 5],
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42)
           .skip(10));
-  AsyncExpect.events(
-      [3, 5],
-      [2, 4],
-      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42)
+  AsyncExpect.events([3, 5], [2, 4],
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42)
           .skip(1));
-  AsyncExpect.events(
-      [5],
-      [2, 4],
-      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42)
+  AsyncExpect.events([5], [2, 4],
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42)
           .skip(2));
 }
diff --git a/LibTest/async/Stream/takeWhile_A01_t02.test.dart b/LibTest/async/Stream/takeWhile_A01_t02.test.dart
index 7fe861a..896692a 100644
--- a/LibTest/async/Stream/takeWhile_A01_t02.test.dart
+++ b/LibTest/async/Stream/takeWhile_A01_t02.test.dart
@@ -6,8 +6,8 @@
 /// Forwards data events while test is successful.
 /// The returned stream provides the same events as this stream as long as test
 /// returns true for the event data.
-/// The stream is done when either this stream is done, or when this stream first
-/// provides a value that test doesn't accept.
+/// The stream is done when either this stream is done, or when this stream
+/// first provides a value that test doesn't accept.
 /// @description Checks that all error events (which occur before the returned
 /// stream is done) are submitted to the returned stream.
 /// Checks that the resulting stream ends with a done event.
@@ -24,24 +24,30 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3], isError: (_) => true, defVal: 42), (x) => false, [], [1, 2, 3]);
-  check(create([1, 2, 3], isError: (_) => true, defVal: 42), (x) => true, [], [1, 2, 3]);
+  check(create([1, 2, 3], isError: (_) => true, defaultValue: 42), (x) => false,
+      [], [1, 2, 3]);
+  check(create([1, 2, 3], isError: (_) => true, defaultValue: 42), (x) => true,
+      [], [1, 2, 3]);
 
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42), (x) => false, [],
-      [1]);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
+      (x) => false, [], [1]);
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
       (x) => x < 4, [2], [1, 3]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42), (x) => false,
-      [], []);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
+      (x) => false, [], []);
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (x) => x < 4, [1, 3], [2, 4]);
 
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defVal: 42), (x) => true,
-      [4, 5], [1, 2, 3]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defVal: 42), (x) => false, [],
-      [1, 2, 3]);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defVal: 42), (x) => x > 2,
-      [4, 5], [1, 2, 3]);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x > 2, defVal: 42), (x) => x < 3,
-      [1, 2], [3, 4, 5]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defaultValue: 42),
+      (x) => true, [4, 5], [1, 2, 3]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defaultValue: 42),
+      (x) => false, [], [1, 2, 3]);
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defaultValue: 42),
+      (x) => x > 2, [4, 5], [1, 2, 3]);
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x > 2, defaultValue: 42),
+      (x) => x < 3, [1, 2], [3, 4, 5]);
 }
diff --git a/LibTest/async/Stream/take_A01_t02.test.dart b/LibTest/async/Stream/take_A01_t02.test.dart
index 0b45544..16d7a48 100644
--- a/LibTest/async/Stream/take_A01_t02.test.dart
+++ b/LibTest/async/Stream/take_A01_t02.test.dart
@@ -4,10 +4,10 @@
 
 /// @assertion Stream<T> take(int count)
 /// Provides at most the first n values of this stream.
-/// Forwards the first n data events of this stream, and all error events,
-/// to the returned stream, and ends with a done event.
-/// If this stream produces fewer than count values before it's done,
-/// so will the returned stream.
+/// Forwards the first n data events of this stream, and all error events, to
+/// the returned stream, and ends with a done event.
+/// If this stream produces fewer than count values before it's done, so will
+/// the returned stream.
 /// @description Checks that all error events (which are before first n data
 /// events) are submitted to the returned stream. Checks that the resulting
 /// stream ends with a done event.
@@ -18,23 +18,29 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-void check<T>(
+void  check<T>(
     Stream<T> s, int count, List<T> expectedData, List expectedErrors) {
   AsyncExpect.events(expectedData, expectedErrors, s.take(count));
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3], isError: (_) => true, defVal: 42), 0, [], []);
-  check(create([1, 2, 3], isError: (_) => true, defVal: 42), 1, [], [1, 2, 3]);
-  check(create([1, 2, 3], isError: (_) => true, defVal: 42), 10, [], [1, 2, 3]);
+  check(create([1, 2, 3], isError: (_) => true, defaultValue: 42), 0, [], []);
+  check(create([1, 2, 3], isError: (_) => true, defaultValue: 42),
+      1, [], [1, 2, 3]);
+  check(create([1, 2, 3], isError: (_) => true, defaultValue: 42),
+      10, [], [1, 2, 3]);
 
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42), 10, [2, 4],
-      [1, 3, 5]);
-  check(
-      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42), 2, [2, 4], [1, 3]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42), 1, [1], []);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42), 2, [1, 3], [2]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
+      10, [2, 4], [1, 3, 5]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
+      2, [2, 4], [1, 3]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
+      1, [1], []);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
+      2, [1, 3], [2]);
 
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defVal: 42), 1, [4], [1, 2, 3]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x > 2, defVal: 42), 2, [1, 2], []);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x < 4, defaultValue: 42),
+      1, [4], [1, 2, 3]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x > 2, defaultValue: 42),
+      2, [1, 2], []);
 }
diff --git a/LibTest/async/Stream/timeout_A01_t02.test.dart b/LibTest/async/Stream/timeout_A01_t02.test.dart
index e335514..91fc53b 100644
--- a/LibTest/async/Stream/timeout_A01_t02.test.dart
+++ b/LibTest/async/Stream/timeout_A01_t02.test.dart
@@ -22,10 +22,10 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42), [],
-      [1, 2, 3, 4, 5]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42),
+      [], [1, 2, 3, 4, 5]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       [1, 3, 5], [2, 4]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
       [2, 4], [1, 3, 5]);
 }
diff --git a/LibTest/async/Stream/timeout_A02_t01.test.dart b/LibTest/async/Stream/timeout_A02_t01.test.dart
index 6708c9c..06170b8 100644
--- a/LibTest/async/Stream/timeout_A02_t01.test.dart
+++ b/LibTest/async/Stream/timeout_A02_t01.test.dart
@@ -21,9 +21,9 @@
 void test(CreateStreamFunction create) {
   int count = 0;
   Stream s1 = create(["a", "b", "c"]);
-  Stream s2 = s1.asyncMap((x) => new Future.delayed(durationMs(100), () => x));
+  Stream s2 = s1.asyncMap((x) => new Future.delayed(durationInMilliseconds(100), () => x));
   Stream s3 = s2.timeout(
-      durationMs(10),
+      durationInMilliseconds(10),
       onTimeout: (EventSink sink) => sink.add(count++)
   );
   AsyncExpect.data([0, "a", 1, "b", 2, "c"], s3);
diff --git a/LibTest/async/Stream/timeout_A02_t02.test.dart b/LibTest/async/Stream/timeout_A02_t02.test.dart
index 5c1fe6e..22a1752 100644
--- a/LibTest/async/Stream/timeout_A02_t02.test.dart
+++ b/LibTest/async/Stream/timeout_A02_t02.test.dart
@@ -22,7 +22,7 @@
   // delay for 100 ms and throw error if element starts with '!'
   Stream s2 = s.asyncMap(
                           (x) => new Future.delayed(
-                              durationMs(100),
+                              durationInMilliseconds(100),
                               () {
                                 if (x is String && x.startsWith("!")){
                                   throw x;
@@ -32,7 +32,7 @@
                           )
   );
   Stream s3 = s2.timeout(
-      durationMs(10),
+      durationInMilliseconds(10),
       onTimeout: (EventSink sink) => sink.add(count++)
   );
   List actualEvents = [];
diff --git a/LibTest/async/Stream/timeout_A03_t01.test.dart b/LibTest/async/Stream/timeout_A03_t01.test.dart
index a35dcff..182fa85 100644
--- a/LibTest/async/Stream/timeout_A03_t01.test.dart
+++ b/LibTest/async/Stream/timeout_A03_t01.test.dart
@@ -20,8 +20,8 @@
 void test(CreateStreamFunction create) {
   int count = 0;
   Stream s1 = create(["a", "b", "c"]);
-  Stream s2 = s1.asyncMap((x) => new Future.delayed(durationMs(100), () => x));
-  Stream s3 = s2.timeout(durationMs(10));
+  Stream s2 = s1.asyncMap((x) => new Future.delayed(durationInMilliseconds(100), () => x));
+  Stream s3 = s2.timeout(durationInMilliseconds(10));
   List actual = [];
   asyncStart();
   s3.listen(
diff --git a/LibTest/async/Stream/timeout_A03_t02.test.dart b/LibTest/async/Stream/timeout_A03_t02.test.dart
index 180b9e9..e344982 100644
--- a/LibTest/async/Stream/timeout_A03_t02.test.dart
+++ b/LibTest/async/Stream/timeout_A03_t02.test.dart
@@ -23,7 +23,7 @@
   // delay for 100 ms and throw error if element starts with '!'
   Stream s2 = s.asyncMap(
                           (x) => new Future.delayed(
-                              durationMs(100),
+                              durationInMilliseconds(100),
                               () {
                                 if (x is String && x.startsWith("!")){
                                   throw x;
@@ -32,7 +32,7 @@
                               }
                           )
   );
-  Stream s3 = s2.timeout(durationMs(10));
+  Stream s3 = s2.timeout(durationInMilliseconds(10));
   List actualEvents = [];
   asyncStart();
   s3.listen(
diff --git a/LibTest/async/Stream/timeout_A05_t01.test.dart b/LibTest/async/Stream/timeout_A05_t01.test.dart
index 8bd2215..0d11deb 100644
--- a/LibTest/async/Stream/timeout_A05_t01.test.dart
+++ b/LibTest/async/Stream/timeout_A05_t01.test.dart
@@ -14,10 +14,10 @@
 import "../../../Utils/expect.dart";
 
 void check<T>(Stream<T> s, T timeoutValue) {
-  Expect.equals(s.isBroadcast, s.timeout(durationMs(10)).isBroadcast);
+  Expect.equals(s.isBroadcast, s.timeout(durationInMilliseconds(10)).isBroadcast);
   Expect.equals(s.isBroadcast,
                 s.timeout(
-                    durationMs(10),
+                    durationInMilliseconds(10),
                     onTimeout:(EventSink<T> sink) => sink.add(timeoutValue)
                 ).isBroadcast
   );
diff --git a/LibTest/async/Stream/transform_A01_t01.test.dart b/LibTest/async/Stream/transform_A01_t01.test.dart
index 1aebc61..c6938dd 100644
--- a/LibTest/async/Stream/transform_A01_t01.test.dart
+++ b/LibTest/async/Stream/transform_A01_t01.test.dart
@@ -30,16 +30,17 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3, 4, 5], defVal: 42), passThrough, [1, 2, 3, 4, 5], []);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42), passThrough,
-      [2, 4], [1, 3, 5]);
-  check(create([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42), passThrough, [],
-      [1, 2, 3, 4, 5]);
+  check(create([1, 2, 3, 4, 5], defaultValue: 42),
+      passThrough, [1, 2, 3, 4, 5], []);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
+      passThrough, [2, 4], [1, 3, 5]);
+  check(create([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42),
+      passThrough, [], [1, 2, 3, 4, 5]);
 
-  check(create([1, 2, 3, 4, 5], defVal: 42), doubleDataNegateError,
+  check(create([1, 2, 3, 4, 5], defaultValue: 42), doubleDataNegateError,
       [1, 1, 2, 2, 3, 3, 4, 4, 5, 5], []);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isOdd, defaultValue: 42),
       doubleDataNegateError, [2, 2, 4, 4], [-1, -3, -5]);
-  check(create([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42), doubleDataNegateError,
-      [], [-1, -2, -3, -4, -5]);
+  check(create([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42),
+      doubleDataNegateError, [], [-1, -2, -3, -4, -5]);
 }
diff --git a/LibTest/async/Stream/where_A01_t02.test.dart b/LibTest/async/Stream/where_A01_t02.test.dart
index 8db640e..0f0ed2f 100644
--- a/LibTest/async/Stream/where_A01_t02.test.dart
+++ b/LibTest/async/Stream/where_A01_t02.test.dart
@@ -21,14 +21,16 @@
 }
 
 void test(CreateStreamWithErrorsFunction create) {
-  check(create([1, 2, 3, 4, 5], isError: (x) => true, defVal: 42), (e) => true,
-      [], [1, 2, 3, 4, 5]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check(create([1, 2, 3, 4, 5], isError: (x) => true, defaultValue: 42),
+      (e) => true, [], [1, 2, 3, 4, 5]);
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (e) => true, [1, 3, 5], [2, 4]);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (e) => e > 1, [3, 5], [2, 4]);
-  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (e) => false, [], [2, 4]);
-  check<int>(create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defVal: 42),
+  check<int>(
+      create<int>([1, 2, 3, 4, 5], isError: (x) => x.isEven, defaultValue: 42),
       (e) => throw e, [], [1, 2, 3, 4, 5]);
 }
diff --git a/LibTest/async/StreamController/StreamController.broadcast_A07_t03.dart b/LibTest/async/StreamController/StreamController.broadcast_A07_t03.dart
index 58b9dcb..dafd54b 100644
--- a/LibTest/async/StreamController/StreamController.broadcast_A07_t03.dart
+++ b/LibTest/async/StreamController/StreamController.broadcast_A07_t03.dart
@@ -32,7 +32,7 @@
   );
 
   int i = 0, k = 0;
-  new Timer.periodic(durationMs(100), (Timer timer) {
+  new Timer.periodic(durationInMilliseconds(100), (Timer timer) {
     new Future.value(subscriptions[i].cancel()).then(
       (_) {
         Expect.equals((++k < 5) ? 0 : 1, onCancelCallCount);
diff --git a/LibTest/async/StreamController/StreamController.broadcast_A08_t02.dart b/LibTest/async/StreamController/StreamController.broadcast_A08_t02.dart
index 6b89444..24346c1 100644
--- a/LibTest/async/StreamController/StreamController.broadcast_A08_t02.dart
+++ b/LibTest/async/StreamController/StreamController.broadcast_A08_t02.dart
@@ -21,7 +21,7 @@
 
 Future unsubscribe(List<StreamSubscription> subscriptions, int count) {
   count--;
-  return new Future.delayed(durationMs(50), () => subscriptions[count].cancel())
+  return new Future.delayed(durationInMilliseconds(50), () => subscriptions[count].cancel())
       .then((_) {
     if (count > 0) {
       return unsubscribe(subscriptions, count);
diff --git a/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A01_t02.dart b/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A01_t02.dart
index 1589bfb..6bdf08c 100644
--- a/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A01_t02.dart
+++ b/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A01_t02.dart
@@ -18,7 +18,8 @@
 import "dart:async";
 import "../Stream/allTests_A02.lib.dart";
 
-Stream<T> create<T>(Iterable<T> data, {bool isError(T element)?, T? defVal}) {
+Stream<T> create<T>(
+    Iterable<T> data, {bool isError(T element)?, T? defaultValue}) {
   StreamController<T>? sc;
   sc = new StreamController<T>.broadcast(
     onListen:() {
diff --git a/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A02_t02.dart b/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A02_t02.dart
index f4fc9b2..1598dcd 100644
--- a/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A02_t02.dart
+++ b/LibTest/async/StreamController/StreamController.broadcast_Stream_all_A02_t02.dart
@@ -18,7 +18,8 @@
 import "dart:async";
 import "../Stream/allTests_A02.lib.dart";
 
-Stream<T> create<T>(Iterable<T> data, {bool isError(T element)?, T? defVal}) {
+Stream<T> create<T>(
+    Iterable<T> data, {bool isError(T element)?, T? defaultValue}) {
   StreamController<T>? sc;
   sc = new StreamController<T>.broadcast(
     sync: true,
diff --git a/LibTest/async/StreamController/StreamController_A07_t01.dart b/LibTest/async/StreamController/StreamController_A07_t01.dart
index 406ac2d..7b8ffab 100644
--- a/LibTest/async/StreamController/StreamController_A07_t01.dart
+++ b/LibTest/async/StreamController/StreamController_A07_t01.dart
@@ -19,7 +19,7 @@
   bool onCancelFutureComplete = false;
   StreamController controller = new StreamController(
     onCancel: () => new Future.delayed(
-      durationMs(100),
+      durationInMilliseconds(100),
       () {
         onCancelFutureComplete = true;
       }
diff --git a/LibTest/async/StreamController/stream_all_A01_t02.dart b/LibTest/async/StreamController/stream_all_A01_t02.dart
index bfedd63..14d415a 100644
--- a/LibTest/async/StreamController/stream_all_A01_t02.dart
+++ b/LibTest/async/StreamController/stream_all_A01_t02.dart
@@ -10,7 +10,8 @@
 import "dart:async";
 import "../Stream/allTests_A02.lib.dart";
 
-Stream<T> create<T>(Iterable<T> data, {bool isError(T element)?, T? defVal}) {
+Stream<T> create<T>(
+    Iterable<T> data, {bool isError(T element)?, T? defaultValue}) {
   StreamController<T> sc = new StreamController<T>();
   for (T e in data) {
     if (isError != null && isError(e)) {
diff --git a/LibTest/async/StreamController/stream_all_A02_t02.dart b/LibTest/async/StreamController/stream_all_A02_t02.dart
index 33f9989..ab2025e 100644
--- a/LibTest/async/StreamController/stream_all_A02_t02.dart
+++ b/LibTest/async/StreamController/stream_all_A02_t02.dart
@@ -10,7 +10,7 @@
 import "dart:async";
 import "../Stream/allTests_A02.lib.dart";
 
-Stream<T> create<T>(Iterable<T> data, {bool isError(T element)?, T? defVal}) {
+Stream<T> create<T>(Iterable<T> data, {bool isError(T element)?, T? defaultValue}) {
   StreamController<T>? sc;
   sc = new StreamController<T>(
     sync: true,
diff --git a/LibTest/async/Timer/Timer.periodic_A01_t01.dart b/LibTest/async/Timer/Timer.periodic_A01_t01.dart
index 1de955a..40bc43e 100644
--- a/LibTest/async/Timer/Timer.periodic_A01_t01.dart
+++ b/LibTest/async/Timer/Timer.periodic_A01_t01.dart
@@ -15,7 +15,7 @@
 main() {
   int times = 10;
   int count = 0;
-  Duration delay = durationMs(20);
+  Duration delay = durationInMilliseconds(20);
   Stopwatch sw = new Stopwatch();
   sw.start();
 
diff --git a/LibTest/async/Timer/Timer.periodic_A02_t01.dart b/LibTest/async/Timer/Timer.periodic_A02_t01.dart
index 810ba71..a25a3f3 100644
--- a/LibTest/async/Timer/Timer.periodic_A02_t01.dart
+++ b/LibTest/async/Timer/Timer.periodic_A02_t01.dart
@@ -14,7 +14,7 @@
   int times = 5;
   int count = 0;
   asyncStart();
-  new Timer.periodic(durationMs(delay), (Timer timer) {
+  new Timer.periodic(durationInMilliseconds(delay), (Timer timer) {
     count++;
     if (count == times) {
       timer.cancel();
diff --git a/LibTest/async/Timer/Timer_A01_t01.dart b/LibTest/async/Timer/Timer_A01_t01.dart
index 4ba357b..2f7eff8 100644
--- a/LibTest/async/Timer/Timer_A01_t01.dart
+++ b/LibTest/async/Timer/Timer_A01_t01.dart
@@ -12,7 +12,7 @@
 import "../../../Utils/expect.dart";
 
 check(int delayms) {
-  Duration delay = durationMs(delayms);
+  Duration delay = durationInMilliseconds(delayms);
   Stopwatch sw = new Stopwatch();
   sw.start();
 
diff --git a/LibTest/async/Timer/Timer_A02_t01.dart b/LibTest/async/Timer/Timer_A02_t01.dart
index 3b52f22..920e010 100644
--- a/LibTest/async/Timer/Timer_A02_t01.dart
+++ b/LibTest/async/Timer/Timer_A02_t01.dart
@@ -14,7 +14,7 @@
   bool seen = false;
 
   asyncStart();
-  new Timer(durationMs(delayms), () {
+  new Timer(durationInMilliseconds(delayms), () {
     Expect.isFalse(seen);
     seen = true;
     asyncEnd();
diff --git a/LibTest/async/Timer/cancel_A01_t01.dart b/LibTest/async/Timer/cancel_A01_t01.dart
index 1b5ae44..b2f863c 100644
--- a/LibTest/async/Timer/cancel_A01_t01.dart
+++ b/LibTest/async/Timer/cancel_A01_t01.dart
@@ -14,14 +14,14 @@
   int delay = 20;
   int count = 0;
 
-  Timer timer = new Timer.periodic(durationMs(delay), (Timer t) {
+  Timer timer = new Timer.periodic(durationInMilliseconds(delay), (Timer t) {
       count++;
     }
   );
   timer.cancel();
   
   asyncStart();
-  new Timer(durationMs(delay * 3), () {
+  new Timer(durationInMilliseconds(delay * 3), () {
     Expect.equals(count, 0);
     asyncEnd();
   });
diff --git a/LibTest/async/Timer/cancel_A01_t02.dart b/LibTest/async/Timer/cancel_A01_t02.dart
index fe69d42..908c7ac 100644
--- a/LibTest/async/Timer/cancel_A01_t02.dart
+++ b/LibTest/async/Timer/cancel_A01_t02.dart
@@ -14,14 +14,14 @@
   int delay = 20;
   int count = 0;
 
-  Timer timer = new Timer(durationMs(delay), () {
+  Timer timer = new Timer(durationInMilliseconds(delay), () {
       count++;
     }
   );
   timer.cancel();
   
   asyncStart();
-  new Timer(durationMs(delay * 3), () {
+  new Timer(durationInMilliseconds(delay * 3), () {
     Expect.equals(count, 0);
     asyncEnd();
   });
diff --git a/LibTest/async/Timer/isActive_A01_t01.dart b/LibTest/async/Timer/isActive_A01_t01.dart
index a1d0853..8993628 100644
--- a/LibTest/async/Timer/isActive_A01_t01.dart
+++ b/LibTest/async/Timer/isActive_A01_t01.dart
@@ -17,7 +17,7 @@
 check(int delayms) {
   asyncStart();
   Timer? t;
-  t = new Timer(durationMs(delayms), () {
+  t = new Timer(durationInMilliseconds(delayms), () {
     Expect.isFalse(t!.isActive);
     asyncEnd();
   });
diff --git a/LibTest/async/Timer/isActive_A01_t02.dart b/LibTest/async/Timer/isActive_A01_t02.dart
index a50030e..776a79a 100644
--- a/LibTest/async/Timer/isActive_A01_t02.dart
+++ b/LibTest/async/Timer/isActive_A01_t02.dart
@@ -19,7 +19,7 @@
   int count = 0;
 
   asyncStart();
-  Timer t = new Timer.periodic(durationMs(delay), (Timer timer) {
+  Timer t = new Timer.periodic(durationInMilliseconds(delay), (Timer timer) {
     count++;
     Expect.isTrue(timer.isActive);
     if (count == times) {
diff --git a/LibTest/async/Timer/run_A01_t01.dart b/LibTest/async/Timer/run_A01_t01.dart
index 88309e9..07dbb59 100644
--- a/LibTest/async/Timer/run_A01_t01.dart
+++ b/LibTest/async/Timer/run_A01_t01.dart
@@ -19,7 +19,7 @@
     count++;
   });
 
-  new Timer(durationMs(100), () {
+  new Timer(durationInMilliseconds(100), () {
     Expect.equals(1, count);
     asyncEnd();
   });
diff --git a/LibTest/core/ArgumentError/ArgumentError.notNull_A01_t02.dart b/LibTest/core/ArgumentError/ArgumentError.notNull_A01_t02.dart
index e706468..20261c2 100644
--- a/LibTest/core/ArgumentError/ArgumentError.notNull_A01_t02.dart
+++ b/LibTest/core/ArgumentError/ArgumentError.notNull_A01_t02.dart
@@ -12,6 +12,6 @@
  
 main() {
   ArgumentError err = new ArgumentError.notNull();
-  Expect.isNull(null, err.name);
+  Expect.isNull(null, err.name ?? 'unnamed error');
   Expect.equals("Must not be null", err.message);
 }
diff --git a/LibTest/core/Stopwatch/elapsedMicroseconds_A01_t01.dart b/LibTest/core/Stopwatch/elapsedMicroseconds_A01_t01.dart
index 9ead733..d796277 100644
--- a/LibTest/core/Stopwatch/elapsedMicroseconds_A01_t01.dart
+++ b/LibTest/core/Stopwatch/elapsedMicroseconds_A01_t01.dart
@@ -12,7 +12,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(10);
+Duration delay = durationInMilliseconds(10);
 Stopwatch sw = new Stopwatch();
 int count = 5;
 
diff --git a/LibTest/core/Stopwatch/elapsedMilliseconds_A01_t01.dart b/LibTest/core/Stopwatch/elapsedMilliseconds_A01_t01.dart
index ec74786..be2564c 100644
--- a/LibTest/core/Stopwatch/elapsedMilliseconds_A01_t01.dart
+++ b/LibTest/core/Stopwatch/elapsedMilliseconds_A01_t01.dart
@@ -12,7 +12,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(10);
+Duration delay = durationInMilliseconds(10);
 Stopwatch sw = new Stopwatch();
 int count = 5;
 
diff --git a/LibTest/core/Stopwatch/elapsedTicks_A01_t01.dart b/LibTest/core/Stopwatch/elapsedTicks_A01_t01.dart
index e97c232..b464a66 100644
--- a/LibTest/core/Stopwatch/elapsedTicks_A01_t01.dart
+++ b/LibTest/core/Stopwatch/elapsedTicks_A01_t01.dart
@@ -16,7 +16,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(10);
+Duration delay = durationInMilliseconds(10);
 Stopwatch sw = new Stopwatch();
 int count = 5;
 int e0 = 0;
diff --git a/LibTest/core/Stopwatch/elapsedTicks_A01_t02.dart b/LibTest/core/Stopwatch/elapsedTicks_A01_t02.dart
index 4dea05a..f3fe0fa 100644
--- a/LibTest/core/Stopwatch/elapsedTicks_A01_t02.dart
+++ b/LibTest/core/Stopwatch/elapsedTicks_A01_t02.dart
@@ -16,7 +16,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(10);
+Duration delay = durationInMilliseconds(10);
 Stopwatch sw = new Stopwatch();
 int count = 5;
 int e0 = 0;
diff --git a/LibTest/core/Stopwatch/elapsedTicks_A01_t03.dart b/LibTest/core/Stopwatch/elapsedTicks_A01_t03.dart
index 2fcaab9..fde04ba 100644
--- a/LibTest/core/Stopwatch/elapsedTicks_A01_t03.dart
+++ b/LibTest/core/Stopwatch/elapsedTicks_A01_t03.dart
@@ -16,7 +16,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(10);
+Duration delay = durationInMilliseconds(10);
 Stopwatch sw = new Stopwatch();
 int count = 5;
 
diff --git a/LibTest/core/Stopwatch/elapsed_A01_t01.dart b/LibTest/core/Stopwatch/elapsed_A01_t01.dart
index 4f573e4..c3915f9 100644
--- a/LibTest/core/Stopwatch/elapsed_A01_t01.dart
+++ b/LibTest/core/Stopwatch/elapsed_A01_t01.dart
@@ -11,7 +11,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 Duration e0 = new Duration();
 
diff --git a/LibTest/core/Stopwatch/elapsed_A01_t02.dart b/LibTest/core/Stopwatch/elapsed_A01_t02.dart
index 5185455..681718a 100644
--- a/LibTest/core/Stopwatch/elapsed_A01_t02.dart
+++ b/LibTest/core/Stopwatch/elapsed_A01_t02.dart
@@ -11,7 +11,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 Duration e0 = new Duration();
 
diff --git a/LibTest/core/Stopwatch/elapsed_A01_t03.dart b/LibTest/core/Stopwatch/elapsed_A01_t03.dart
index 5dbebe8..314f345 100644
--- a/LibTest/core/Stopwatch/elapsed_A01_t03.dart
+++ b/LibTest/core/Stopwatch/elapsed_A01_t03.dart
@@ -11,7 +11,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 
 main() {
diff --git a/LibTest/core/Stopwatch/isRunning_A01_t01.dart b/LibTest/core/Stopwatch/isRunning_A01_t01.dart
index 4e9ebb1..1ff3a92 100644
--- a/LibTest/core/Stopwatch/isRunning_A01_t01.dart
+++ b/LibTest/core/Stopwatch/isRunning_A01_t01.dart
@@ -11,7 +11,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(20);
+Duration delay = durationInMilliseconds(20);
 Stopwatch sw = new Stopwatch();
 
 main() {
diff --git a/LibTest/core/Stopwatch/reset_A01_t01.dart b/LibTest/core/Stopwatch/reset_A01_t01.dart
index e62fbb4..50249e8 100644
--- a/LibTest/core/Stopwatch/reset_A01_t01.dart
+++ b/LibTest/core/Stopwatch/reset_A01_t01.dart
@@ -11,7 +11,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 int e0 = 0;
 
diff --git a/LibTest/core/Stopwatch/start_A01_t01.dart b/LibTest/core/Stopwatch/start_A01_t01.dart
index 168930d..c084a33 100644
--- a/LibTest/core/Stopwatch/start_A01_t01.dart
+++ b/LibTest/core/Stopwatch/start_A01_t01.dart
@@ -15,7 +15,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 int e0 = 0;
 
diff --git a/LibTest/core/Stopwatch/start_A01_t02.dart b/LibTest/core/Stopwatch/start_A01_t02.dart
index 4c144d1..8f98c32 100644
--- a/LibTest/core/Stopwatch/start_A01_t02.dart
+++ b/LibTest/core/Stopwatch/start_A01_t02.dart
@@ -15,7 +15,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 int e0 = 0;
 
diff --git a/LibTest/core/Stopwatch/start_A01_t03.dart b/LibTest/core/Stopwatch/start_A01_t03.dart
index 63aedba..4396a25 100644
--- a/LibTest/core/Stopwatch/start_A01_t03.dart
+++ b/LibTest/core/Stopwatch/start_A01_t03.dart
@@ -15,7 +15,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(50);
+Duration delay = durationInMilliseconds(50);
 Stopwatch sw = new Stopwatch();
 int e0 = 0;
 
diff --git a/LibTest/core/Stopwatch/stop_A01_t01.dart b/LibTest/core/Stopwatch/stop_A01_t01.dart
index dfa7291..f328623 100644
--- a/LibTest/core/Stopwatch/stop_A01_t01.dart
+++ b/LibTest/core/Stopwatch/stop_A01_t01.dart
@@ -13,7 +13,7 @@
 import "dart:async";
 import "../../../Utils/expect.dart";
 
-Duration delay = durationMs(10);
+Duration delay = durationInMilliseconds(10);
 Stopwatch sw = new Stopwatch();
 int count = 5;
 int ticks = -1;
diff --git a/LibTest/io/RawDatagramSocket/timeout_A06_t01.dart b/LibTest/io/RawDatagramSocket/timeout_A06_t01.dart
index fd91a43..609373a 100644
--- a/LibTest/io/RawDatagramSocket/timeout_A06_t01.dart
+++ b/LibTest/io/RawDatagramSocket/timeout_A06_t01.dart
@@ -51,7 +51,7 @@
       });
 
       Stream bcs = receiver.asBroadcastStream();
-      Stream s = bcs.timeout(durationMs(1));
+      Stream s = bcs.timeout(durationInMilliseconds(1));
       s.listen((event) {
         list1.add(event);
         receiver.receive();
diff --git a/LibTest/isolate/ReceivePort/asBroadcastStream_A04_t03.dart b/LibTest/isolate/ReceivePort/asBroadcastStream_A04_t03.dart
index a985ee7..88e5387 100644
--- a/LibTest/isolate/ReceivePort/asBroadcastStream_A04_t03.dart
+++ b/LibTest/isolate/ReceivePort/asBroadcastStream_A04_t03.dart
@@ -71,5 +71,5 @@
     }
   }
 
-  timer = new Timer.periodic(durationMs(10), addSubscribersIfNeeded);
+  timer = new Timer.periodic(durationInMilliseconds(10), addSubscribersIfNeeded);
 }
diff --git a/Utils/async_utils.dart b/Utils/async_utils.dart
index 2d5e5ed..c65ca77 100644
--- a/Utils/async_utils.dart
+++ b/Utils/async_utils.dart
@@ -2,22 +2,22 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-part of Expect;
+part of 'expect.dart';
 
-const ONE_MS = const Duration(milliseconds: 1);
+const oneMillisecond = const Duration(milliseconds: 1);
 
 typedef CreateStreamFunction = Stream<T> Function<T>(Iterable<T> values);
 typedef CreateStreamWithErrorsFunction =
     Stream<T> Function<T>(Iterable<T> values,
-        {bool Function(T element)? isError, required T defVal});
+        {bool Function(T element)? isError, required T defaultValue});
 
-Duration durationMs(delay) {
-  return delay == null ? Duration.zero : ONE_MS * delay;
+Duration durationInMilliseconds(delay) {
+  return delay == null ? Duration.zero : oneMillisecond * delay;
 }
 
 Future runLater(void action(), [int delay = 0]) {
   asyncStart();
-  return new Future.delayed(durationMs(delay), (){
+  return Future.delayed(durationInMilliseconds(delay), () {
     action();
     asyncEnd();
   });
@@ -31,10 +31,9 @@
   });
 }
 
-/// Let the test driver know the test is asynchronous and
-/// continues after the method main() exits.
-/// see co19 issue #423
-/// http://code.google.com/p/co19/issues/detail?id=423
+/// Let the test driver know the test is asynchronous and continues after the
+/// method main() exits.
+/// See http://code.google.com/p/co19/issues/detail?id=423
 
 Completer _completer = new Completer();
 Future asyncCompleted = _completer.future;
@@ -48,16 +47,13 @@
 
 void  asyncStart() {
   _asyncCounter++;
-//  print("asyncStart");
 }
 
 void  asyncMultiStart(int delta) {
-//  print("asyncMultiStart $delta");
   _asyncCounter += delta;
 }
 
 void  asyncEnd() {
-//  print("asyncEnd");
   Expect.isFalse(_asyncCounter == 0, "asyncEnd: _asyncCounter==0");
   _asyncCounter--;
   if (_asyncCounter == 0) {
@@ -93,17 +89,19 @@
 }
 /*----------------------------*/
 
-///  asyncTest is intended for executing tests with asynchronous nature.
-///  If [setup] is provided, it will be executed first in order to prepare
+/// [asyncTest] is intended for executing tests with asynchronous nature.
+///
+/// If [setup] is provided, it will be executed first in order to prepare
 /// necessary environment for the test (i.e. create some files, start some
 /// services, etc). The [setup] may return some value, which will be passed to
 /// [test] and to [cleanup].
-///  [test] is main test code. It should return Future instance, which completes
-/// when test is over. The future may complete with error, in this case the whole
-/// test will fail.
-///   If [cleanup] is provided it will be executed after Future returned by [test]
-/// is completed. [cleanup] is always called, regardless of test's status.
-
+///
+/// [test] is the main test code. It should return [Future] instance, which
+/// completes when test is over. The future may complete with error, in this
+/// case the whole test will fail.
+///
+/// If [cleanup] is provided it will be executed after [Future] returned by
+/// [test] is completed. [cleanup] is always called, regardless of test status.
 void asyncTest<T>(Future test(T? value), {required Future<T> setup(),
     required void cleanup(T? value)}) {
   asyncStart();
@@ -117,28 +115,27 @@
   });
 }
 
-/// AsyncExpect is intended for async test to ease checking
-/// Future completion value and checking Stream content.
-
+/// [AsyncExpect] is intended for async test to ease checking [Future]
+/// completion value and checking Stream content.
 class AsyncExpect {
 
-/// Checks whether the given future completes with expected value.
-/// Returns the Future, that may be used for test cleanup via method
-/// whenComplete(). If checks are passed, the returned future completes
-/// the same way as supplied one. Otherwise, the returned future completes
-/// with error.
-  static Future<T> value<T>(T expected, Future<T> future, [String? reason = null]) {
-    if (reason == null){
-      reason = StackTrace.current.toString();
-    }
+  /// Checks whether the given future completes with expected value.
+  ///
+  /// Returns [Future], that may be used for test cleanup via method
+  /// [whenComplete]. If checks are passed, the returned future completes the
+  /// same way as a supplied one. Otherwise, the returned future completes with
+  /// error.
+  static Future<T> value<T>(
+      T expected, Future<T> future, [String? reason]) {
+    String msg = reason ?? StackTrace.current.toString();
     asyncStart();
     return future.then((T value){
       if (expected is List) {
-        Expect.listEquals(expected, value, reason);
+        Expect.listEquals(expected, value, msg);
       } else if (expected is Set) {
-        Expect.setEquals(expected, value as Iterable<Object?>, reason);
+        Expect.setEquals(expected, value as Iterable<Object?>, msg);
       } else {
-        Expect.equals(expected, value, reason);
+        Expect.equals(expected, value, msg);
       }
       asyncEnd();
       return value;
@@ -146,27 +143,26 @@
   }
 
 
-/// Checks whether the given future completes with expected error.
-/// Returns the Future, that may be used for test cleanup via method
-/// whenComplete(). If checks are passed, the returned future completes
-/// the same way as supplied one. Otherwise, the returned future completes
-/// with error.
-  static Future<T?> error<T>(Object error, Future<T> future, [String? reason = null]) {
-    if (reason == null){
-      reason = StackTrace.current.toString();
-    }
+  /// Checks whether the given future completes with expected error.
+  ///
+  /// Returns [Future], that may be used for test cleanup via method
+  /// [whenComplete]. If checks are passed, the returned future completes the
+  /// same way as a supplied one. Otherwise, the returned future completes
+  /// with error.
+  static Future<T?> error<T>(
+      Object error, Future<T> future, [String? reason]) {
+    String msg = reason ?? StackTrace.current.toString();
     asyncStart();
     return future.then(
       (_) {
-        Expect.fail("The future is expected to complete with error $reason");
+        Expect.fail("The future is expected to complete with error $msg");
         return future;
       },
-      onError: (e) {
-        // print("On error called");
+       onError: (e) {
         if (error is Function) {
-          Expect.isTrue(Function.apply(error, [e]), reason);
+          Expect.isTrue(Function.apply(error, [e]), msg);
         } else {
-          Expect.equals(error, e, reason);
+          Expect.equals(error, e, msg);
         }
         asyncEnd();
         return null;
@@ -174,13 +170,12 @@
     );
   }
 
-/// Checks whether the given stream contains expected data events.
-/// Any error in the stream is unexpected and wil fail the test.
-  static Future<bool> data<T>(List<T> data, Stream<T> stream, [String? reason = null]) {
-    if (reason == null){
-      reason = StackTrace.current.toString();
-    }
-    Completer<bool> completer = new Completer<bool>();
+  /// Checks whether the given stream contains expected data events.
+  /// Any error in the stream is unexpected and wil fail the test.
+  static Future<bool> data<T>(
+      List<T> data, Stream<T> stream, [String? reason]) {
+    String msg = reason ?? StackTrace.current.toString();
+    Completer<bool> completer = Completer<bool>();
     List<T> actual = [];
     asyncStart();
     stream.listen(
@@ -188,7 +183,7 @@
           actual.add(value);
         },
         onDone: () {
-          Expect.listEquals(data, actual, reason);
+          Expect.listEquals(data, actual, msg);
           asyncEnd();
           completer.complete(true);
         }
@@ -196,11 +191,10 @@
     return completer.future;
   }
 
-/// Checks whether the given stream contains expected data and error events.
-  static Future<bool> events<T>(List<T> data, List errors, Stream<T> stream, [String? reason = null]) {
-    if (reason == null){
-      reason = StackTrace.current.toString();
-    }
+  /// Checks whether the given stream contains expected data and error events.
+  static Future<bool> events<T>
+        (List<T> data, List errors, Stream<T> stream, [String? reason]) {
+    String msg = reason ?? StackTrace.current.toString();
     Completer<bool> completer = new Completer<bool>();
     List<T> actualData = [];
     List actualErrors = [];
@@ -213,8 +207,8 @@
           actualErrors.add(error);
         },
         onDone: () {
-          Expect.listEquals(data, actualData, reason);
-          Expect.listEquals(errors, actualErrors, reason);
+          Expect.listEquals(data, actualData, msg);
+          Expect.listEquals(errors, actualErrors, msg);
           asyncEnd();
           completer.complete(true);
         }
diff --git a/Utils/dynamic_check.dart b/Utils/dynamic_check.dart
index 4c24046..dc02fc1 100644
--- a/Utils/dynamic_check.dart
+++ b/Utils/dynamic_check.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 library dynamic_check;
-import "expect.dart";
+import 'expect.dart';
 
 checkTypeError(f()) {
   Expect.throws(f, (e) => e is TypeError || e is CastError,
@@ -11,10 +11,9 @@
 }
 
 /// Check that dynamic error occurs. Dart specification (3rd Edition/June 12015)
-/// does not specify what is 'dynamic erros'
+/// does not specify what is 'dynamic errors'
 /// (see https://github.com/dart-lang/sdk/issues/24394 ). So, for now,
-/// this is a stub that checks that Error is thrown
-
+/// this is a stub that checks that [Error] is thrown
 checkDynamicError(f()) {
   Expect.throws(f, (e) => e is Error, "Dynamic Error should be thrown");
 }
diff --git a/Utils/expect.dart b/Utils/expect.dart
index 828c002..26221e3 100644
--- a/Utils/expect.dart
+++ b/Utils/expect.dart
@@ -2,18 +2,17 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library Expect;
-import "dart:async";
-part "expect_common.dart";
-part "async_utils.dart";
-part "lang_feature_check.dart";
+library expect;
+import 'dart:async';
+part 'expect_common.dart';
+part 'async_utils.dart';
+part 'lang_feature_check.dart';
 
-/// Expect is used for tests that do not want to make use of the
-/// Dart unit test library - for example, the core language tests.
-/// Third parties are discouraged from using this, and should use
-/// the expect() function in the unit test library instead for
-/// test assertions.
-
+/// [Expect] is used for tests that do not want to make use of the Dart unit
+/// test library - for example, the core language tests.
+///
+/// Third parties are discouraged from using this, and should use the [expect]
+/// function in the unit test library instead for the test assertions.
 
  void _fail(String message) {
     throw new ExpectException(message);
diff --git a/Utils/expect_common.dart b/Utils/expect_common.dart
index e477e75..4af927e 100644
--- a/Utils/expect_common.dart
+++ b/Utils/expect_common.dart
@@ -2,143 +2,112 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-part of Expect;
-
-/// Expect is used for tests that do not want to make use of the
-/// Dart unit test library - for example, the core language tests.
-/// Third parties are discouraged from using this, and should use
-/// the expect() function in the unit test library instead for
-/// test assertions.
-///
-/// This part contains all except
-///   static void _fail(String message) {}
+part of 'expect.dart';
 
 class Expect {
-  /**
-   * Checks whether the expected and actual values are equal (using `==`).
-   */
-  static void equals(var expected, var actual, [String? reason = null]) {
-    if (expected == actual) return;
-    if ((expected is double) &&
-        (actual is double) &&
-        (expected.isNaN) &&
-        (actual.isNaN)) {
-      return;
+
+  /// Checks whether the expected and actual values are equal using `==`.
+  static void equals(var expected, var actual, [String reason = '']) {
+    if ((expected != actual) &&
+        !((expected is double) &&
+            (actual is double) &&
+            (expected.isNaN) &&
+            (actual.isNaN))) {
+      _fail('Expect.equals(expected: <$expected>, actual: <$actual>$reason) '
+          'fails.');
     }
-    String msg = _getMessage(reason);
-    _fail("Expect.equals(expected: <$expected>, actual: <$actual>$msg) fails.");
   }
 
-  /**
-   * Checks whether the actual value is a bool and its value is true.
-   */
-  static void isTrue(var actual, [String? reason = null]) {
-    if (_identical(actual, true)) return;
-    String msg = _getMessage(reason);
-    _fail("Expect.isTrue($actual$msg) fails.");
-  }
-
-  /**
-   * Checks whether the actual value is a bool and its value is false.
-   */
-  static void isFalse(var actual, [String? reason = null]) {
-    if (_identical(actual, false)) return;
-    String msg = _getMessage(reason);
-    _fail("Expect.isFalse($actual$msg) fails.");
-  }
-
-  /**
-   * Checks whether [actual] is null.
-   */
-  static void isNull(actual, [String? reason = null]) {
-    if (null == actual) return;
-    String msg = _getMessage(reason);
-    _fail("Expect.isNull(actual: <$actual>$msg) fails.");
-  }
-
-  /**
-   * Checks whether [actual] is not null.
-   */
-  static void isNotNull(actual, [String? reason = null]) {
-    if (null != actual) return;
-    String msg = _getMessage(reason);
-    _fail("Expect.isNotNull(actual: <$actual>$msg) fails.");
-  }
-
-  /**
-   * Checks whether the expected and actual values are identical
-   * (using `identical`).
-   */
-  static void identical(var expected, var actual, [String? reason = null]) {
-    if (_identical(expected, actual)) return;
-    String msg = _getMessage(reason);
-    _fail("Expect.identical(expected: <$expected>, actual: <$actual>$msg) "
-        "fails.");
-  }
-
-  // Unconditional failure.
-  static void fail(String? msg) {
-    _fail("Expect.fail('$msg')");
-  }
-
-  /**
-   * Failure if the difference between expected and actual is greater than the
-   * given tolerance. If no tolerance is given, tolerance is assumed to be the
-   * value 4 significant digits smaller than the value given for expected.
-   */
-  static void approxEquals(num expected, num actual,
-      [num? tolerance = null, String? reason = null]) {
-    if (tolerance == null) {
-      tolerance = (expected / 1e4).abs();
+  /// Checks whether the actual value is [bool] and its value is [true].
+  static void isTrue(var actual, [String reason = '']) {
+    if (!_identical(actual, true)) {
+      _fail('Expect.isTrue($actual$reason) fails.');
     }
+  }
+
+  /// Checks whether the actual value is [bool] and its value is [false].
+  static void isFalse(var actual, [String reason = '']) {
+    if (!_identical(actual, false)) {
+      _fail('Expect.isFalse($actual$reason) fails.');
+    }
+  }
+
+  /// Checks whether [actual] is [null].
+  static void isNull(actual, [String reason = '']) {
+    if (null != actual) {
+      _fail('Expect.isNull(actual: <$actual>$reason) fails.');
+    }
+  }
+
+   /// Checks whether [actual] is not [null].
+  static void isNotNull(actual, [String reason = '']) {
+    if (null == actual) {
+      _fail('Expect.isNotNull(actual: <$actual>$reason) fails.');
+    }
+  }
+
+  /// Checks whether the expected and actual values are identical (using
+  /// `identical`).
+  static void identical(var expected, var actual, [String reason = '']) {
+    if (!_identical(expected, actual)) {
+      _fail('Expect.identical(expected: <$expected>, '
+          'actual: <$actual>$reason) fails.');
+    }
+  }
+
+  /// Unconditional failure.
+  static void fail(String reason) {
+    _fail('Expect.fail($reason)');
+  }
+
+  /// Checks whether the difference between expected and actual is greater than
+  /// the given tolerance. If no tolerance is given, tolerance is assumed to be
+  /// a value of the 4 significant digits smaller than the value given for
+  /// [expected].
+  static void approxEquals(
+      num expected, num actual, [num? tolerance, String reason = '']) {
+      tolerance ??= (expected / 1e4).abs();
+
     // Note: use !( <= ) rather than > so we fail on NaNs
-    if ((expected - actual).abs() <= tolerance) return;
-
-    String msg = _getMessage(reason);
-    _fail('Expect.approxEquals(expected:<$expected>, actual:<$actual>, '
-        'tolerance:<$tolerance>$msg) fails');
-  }
-
-  static void notEquals(unexpected, actual, [String? reason = null]) {
-    if (unexpected != actual) return;
-    String msg = _getMessage(reason);
-    _fail("Expect.notEquals(unexpected: <$unexpected>, actual:<$actual>$msg) "
-        "fails.");
-  }
-
-  /**
-   * Specialized equality test for strings. When the strings don't match,
-   * this method shows where the mismatch starts and ends.
-   */
-  static void stringEquals(String? expected, String? actual,
-      [String? reason = null]) {
-    String msg = _getMessage(reason);
-    String defaultMessage =
-        'Expect.stringEquals(expected: <$expected>", <$actual>$msg) fails';
-
-    if (expected == actual) return;
-    if ((expected == null) || (actual == null)) {
-      _fail('$defaultMessage');
-      return;
+    if (!((expected - actual).abs() <= tolerance)) {
+      _fail('Expect.approxEquals(expected:<$expected>, actual:<$actual>, '
+          'tolerance:<$tolerance>$reason) fails');
     }
-    // scan from the left until we find a mismatch
+  }
+
+  /// Checks whether the expected and actual values are not equal.
+  static void notEquals(unexpected, actual, [String reason = '']) {
+    if (unexpected == actual) {
+      _fail('Expect.notEquals(unexpected: <$unexpected>, '
+          'actual:<$actual>$reason) fails.');
+    }
+  }
+
+  /// Specialized equality test for strings. When the strings don't match,
+  /// this method shows where the mismatch starts and ends.
+  static void stringEquals(
+        String? expected, String? actual, [String reason = '']) {
+  String defaultMessage =
+    'Expect.stringEquals(expected: <$expected>, <$actual>$reason) fails';
+  if (expected == actual) return;
+
+  if (expected == null || actual == null) {
+    _fail('$defaultMessage');
+  } else {
+     // Scan from the left until we find a mismatch
     int left = 0;
-    int eLen = expected.length;
-    int aLen = actual.length;
+    int expLength = expected.length;
+    int actLength = actual.length;
     while (true) {
-      if (left == eLen) {
-        assert(left < aLen);
-        String snippet = actual.substring(left, aLen);
+      if (left == expLength) {
+        assert(left < actLength);
+        String snippet = actual.substring(left, actLength);
         _fail('$defaultMessage\nDiff:\n...[  ]\n...[ $snippet ]');
-        return;
-      }
-      if (left == aLen) {
-        assert(left < eLen);
-        String snippet = expected.substring(left, eLen);
+      } else if (left == actLength) {
+        assert(left < expLength);
+        String snippet = expected.substring(left, expLength);
         _fail('$defaultMessage\nDiff:\n...[  ]\n...[ $snippet ]');
-        return;
-      }
-      if (expected[left] != actual[left]) {
+      } else if (expected[left] != actual[left]) {
         break;
       }
       left++;
@@ -147,125 +116,116 @@
     // scan from the right until we find a mismatch
     int right = 0;
     while (true) {
-      if (right == eLen) {
-        assert(right < aLen);
-        String snippet = actual.substring(0, aLen - right);
+      if (right == expLength) {
+        assert(right < actLength);
+        String snippet = actual.substring(0, actLength - right);
         _fail('$defaultMessage\nDiff:\n[  ]...\n[ $snippet ]...');
-        return;
-      }
-      if (right == aLen) {
-        assert(right < eLen);
-        String snippet = expected.substring(0, eLen - right);
+      } else if (right == actLength) {
+        assert(right < expLength);
+        String snippet = expected.substring(0, expLength - right);
         _fail('$defaultMessage\nDiff:\n[  ]...\n[ $snippet ]...');
-        return;
-      }
-      // stop scanning if we've reached the end of the left-to-right match
-      if (eLen - right <= left || aLen - right <= left) {
-        break;
-      }
-      if (expected[eLen - right - 1] != actual[aLen - right - 1]) {
+      } else if ((expLength - right <= left || actLength - right <= left) ||
+          ((expected[expLength - right - 1] != actual[actLength - right - 1]))){
+        // Stop scanning if we've reached the end of the left-to-right match
         break;
       }
       right++;
     }
-    String eSnippet = expected.substring(left, eLen - right);
-    String aSnippet = actual.substring(left, aLen - right);
+
+    String eSnippet = expected.substring(left, expLength - right);
+    String aSnippet = actual.substring(left, actLength - right);
     String diff = '\nDiff:\n...[ $eSnippet ]...\n...[ $aSnippet ]...';
     _fail('$defaultMessage$diff');
   }
+ }
 
-  /**
-   * Checks that every element of [expected] is also in [actual], and that
-   * every element of [actual] is also in [expected].
-   */
-  static void setEquals(Iterable<Object?> expected, Iterable<Object?> actual,
-      [String? reason = null]) {
+  /// Checks that every element of [expected] is also in [actual], and that
+  /// every element of [actual] is also in [expected].
+  static void setEquals(Iterable<Object?> expected,
+      Iterable<Object?> actual, [String reason = '']) {
     final missingSet = new Set.from(expected);
     missingSet.removeAll(actual);
     final extraSet = new Set.from(actual);
     extraSet.removeAll(expected);
 
-    if (extraSet.isEmpty && missingSet.isEmpty) return;
-    String msg = _getMessage(reason);
+    if (!extraSet.isEmpty || !missingSet.isEmpty) {
 
-    StringBuffer sb = new StringBuffer("Expect.setEquals($msg) fails");
-    // Report any missing items.
-    if (!missingSet.isEmpty) {
-      sb.write('\nExpected collection does not contain: ');
-    }
+      StringBuffer buffer = StringBuffer('Expect.setEquals($reason) fails');
+      // Report any missing items.
+      if (!missingSet.isEmpty) {
+        buffer.write('\nExpected collection does not contain: ');
+      }
 
-    for (final val in missingSet) {
-      sb.write('$val ');
-    }
+      for (final val in missingSet) {
+        buffer.write('$val ');
+      }
 
-    // Report any extra items.
-    if (!extraSet.isEmpty) {
-      sb.write('\nExpected collection should not contain: ');
-    }
+      // Report any extra items.
+      if (!extraSet.isEmpty) {
+        buffer.write('\nExpected collection should not contain: ');
+      }
 
-    for (final val in extraSet) {
-      sb.write('$val ');
+      for (final val in extraSet) {
+        buffer.write('$val ');
+      }
+
+      _fail(buffer.toString());
     }
-    _fail(sb.toString());
   }
 
-  /**
-   * Calls the function [f] and verifies that it throws an exception.
-   * The optional [check] function can provide additional validation
-   * that the correct exception is being thrown.  For example, to check
-   * the type of the exception you could write this:
-   *
-   *     Expect.throws(myThrowingFunction, (e) => e is MyException);
-   */
-  static void throws(void f(),
-      [_CheckExceptionFn? check = null, String? reason = null]) {
+  /// Calls the function [func] and verifies that it throws an exception.
+  ///
+  /// The optional [check] function can provide additional validation that
+  /// correct exception is being thrown. For example, to check the type of the
+  /// exception you could write this:
+  ///
+  ///    Expect.throws(myThrowingFunction, (e) => e is MyException);
+  static void throws(
+      void func(), [_CheckExceptionFn? check, String reason = '']) {
     try {
-      f();
-    } catch (e, s) {
-      if (check != null) {
-        if (!check(e)) {
-          String msg = reason == null ? "" : reason;
-          _fail("Expect.throws($msg): Unexpected ${e.runtimeType}('$e')\n$s");
-        }
+      func();
+    } catch (exception, str) {
+      if (check != null && !check(exception)) {
+        _fail('Expect.throws($reason): '
+            'Unexpected ${exception.runtimeType}($exception)\n$str');
       }
       return;
     }
-    String msg = reason == null ? "" : reason;
-    _fail('Expect.throws($msg) fails');
+    _fail('Expect.throws($reason) fails');
   }
 
-  static String _getMessage(String? reason) =>
-      (reason == null) ? "" : ", '$reason'";
-
-  static void listEquals(var expected, var actual, [String? reason = null]) {
-    if (expected is! List) {
-      Expect.fail("expected is not a List:$expected");
+  /// Checks that given lists are equal.
+  static void listEquals(var expected, var actual, [String reason = '']) {
+    if (expected is ! List) {
+      Expect.fail('expected is not a List:$expected');
+    } else if (actual is! List) {
+      Expect.fail('actual is not a List:$expected');
+    } else {
+      deepEquals(expected, actual, reason);
     }
-    if (actual is! List) {
-      Expect.fail("actual is not a List:$expected");
-    }
-    deepEquals(expected, actual, reason);
   }
 
-  static void mapEquals(var expected, var actual, [String? reason = null]) {
+  /// Checks that given maps are equal.
+  static void mapEquals(var expected, var actual, [String reason = '']) {
     if ((expected is! Map) || (actual is! Map)) {
-      Expect.fail("not a Map");
+      Expect.fail('not a Map');
+    } else {
+      deepEquals(expected, actual, reason);
     }
-    deepEquals(expected, actual, reason);
   }
 
-  /** checks that both collections have identical topology and equal primitive elements.
-   *  useful to check cyclic collections passed through ports and streams.
-   */
-  static void deepEquals(var expected, var actual, [String? reason = null]) {
-    Map planned = new Map();
-    Map processed = new Map();
+  /// Checks that both collections have identical topology and equal primitive
+  /// elements. Useful to check cyclic collections passed through ports and
+  /// streams.
+  static void deepEquals(var expected, var actual, [String reason = '']) {
+    Map planned   = Map();
+    Map processed = Map();
 
     void plan2check(var expected, var actual) {
       if (expected == null) {
         Expect.isNull(actual);
       }
-      ;
+
       if ((expected is Map) || (expected is List)) {
         var savedActual = planned[expected];
         if (savedActual != null) {
@@ -277,18 +237,21 @@
         } else {
           // this pair is not yet investigated
           Expect.equals(expected.length, actual.length,
-              "Collections' lengths are not equal: expected length=${expected.length}, actual length=${actual.length}");
+              'Collection lengths are not equal: '
+                  'expected length=${expected.length}, '
+                  'actual length=${actual.length}');
           planned[expected] = actual;
         }
       } else {
-        Expect.equals(expected, actual);
+        Expect.equals(expected, actual, reason);
       }
     }
 
     void runPlanned(var expected, var actual) {
       if (expected is Map) {
         for (var key in expected.keys) {
-//        TODO check that key sets are equivalent. Following method does not work:
+//        TODO check that key sets are equivalent.
+//        The following method does not work:
 //          Expect.isTrue(actual.keys.toSet().remove(key)");
           plan2check(expected[key], actual[key]);
         }
@@ -299,7 +262,7 @@
       } else {
         Expect.fail("only Lists and Maps expected in the plan");
       }
-      // move pair from planned to processed
+      // Move pair from planned to processed
       planned.remove(expected);
       processed[expected] = actual;
     }
@@ -315,19 +278,19 @@
         runPlanned(key, planned[key]);
       }
     } catch (error) {
-      String msg = _getMessage(reason);
-      _fail('deepEquals($expected, $actual, $msg) fails\n   [cause: $error]');
+      _fail('deepEquals($expected, $actual, $reason) fails\n   [cause: $error]');
     }
   }
 
+  // Checks that given шеукфидуы are equal.
   static void iterableEquals(Iterable expected, Iterable actual) {
-    Iterator eit = expected.iterator;
-    Iterator ait = actual.iterator;
-    while (eit.moveNext()) {
-      Expect.isTrue(ait.moveNext());
-      Expect.equals(eit.current, ait.current);
+    Iterator expIterator = expected.iterator;
+    Iterator actIterator = actual.iterator;
+    while (expIterator.moveNext()) {
+      Expect.isTrue(actIterator.moveNext());
+      Expect.equals(expIterator.current, actIterator.current);
     }
-    Expect.isFalse(ait.moveNext());
+    Expect.isFalse(actIterator.moveNext());
   }
 }
 
@@ -343,10 +306,10 @@
 
 /// Is true iff `assert` statements are enabled.
 final bool assertStatementsEnabled = (() {
-  bool result = false;
-  assert(result = true);
-  return result;
-})();
+    bool result = false;
+    assert(result = true);
+    return result;
+  })();
 
 /// Is true iff js compiler is used
 final bool isJS = identical(1.0, 1);
@@ -355,13 +318,15 @@
 class CheckIdentical {
   const CheckIdentical(Object? o1, Object? o2) : assert(identical(o1, o2));
 }
+
 /// Checks that objects are not identical at the compile time
 class CheckNotIdentical {
   const CheckNotIdentical(Object? o1, Object? o2) : assert(!identical(o1, o2));
 }
 
-void checkIs<T>(bool expected, Object? o) {
-  Expect.equals(expected, o is T);
+/// Checks that [obj] object is of the type [T] or not.
+void checkIs<T>(bool expected, Object? obj) {
+  Expect.equals(expected, obj is T);
 }
 
 /// Call this function with `checkIs` as the first parameter to check the type
diff --git a/Utils/lang_feature_check.dart b/Utils/lang_feature_check.dart
index 20096a0..8cd810a 100644
--- a/Utils/lang_feature_check.dart
+++ b/Utils/lang_feature_check.dart
@@ -2,25 +2,26 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-part of Expect;
+part of 'expect.dart';
 
+/// Auxiliary generic function typedef
 typedef F<X> = void Function<Y extends X>();
 
-typedef expected_target = Function<X>();
-
-// Functions for correct type comparison in language feature tests
+/// Returns [F] function with the type parameter of the tested type
 F<X> toF<X>(X x) => <Y extends X>() {};
+
+/// Returns [Type] object for the given [X] type
 Type typeOf<X>() => X;
 
-// Function to check nnbd_top_merge feature
-class CHECK_TOP_MERGE<T> {
+/// Auxiliary function to check nnbd top merge overriding feature
+class CheckTopMerge<T> {
   T Function(T) get f => (x) => x;
 }
 
-// Functions to check least and greatest closures
-// See https://github.com/dart-lang/co19/issues/575#issuecomment-613542349
 Type? _capturedTypeArgument;
 
+// Auxiliary functions to check least and greatest closures
+// See https://github.com/dart-lang/co19/issues/575#issuecomment-613542349
 X captureTypeArgument<X>() {
   _capturedTypeArgument = X;
   throw "Error";
@@ -32,6 +33,6 @@
   return result;
 }
 
-// Sound/Unsound null safety flags (formerly known as weak/strong mode)
+/// Sound/Unsound null safety flags (formerly known as weak/strong mode)
 bool get hasUnsoundNullSafety => const <Null>[] is List<Object>;
 bool get hasSoundNullSafety => !hasUnsoundNullSafety;
diff --git a/Utils/test_mode_check.dart b/Utils/test_mode_check.dart
index 9861bb2..d982afa 100644
--- a/Utils/test_mode_check.dart
+++ b/Utils/test_mode_check.dart
@@ -3,20 +3,21 @@
 // BSD-style license that can be found in the LICENSE file.
 
 library test_mode_check;
-import "dart:io";
+import 'dart:io';
 
-typedef CheckExecutable = bool Function(String s);
+typedef CheckFunction = bool Function(String str);
 
-bool checkMode(CheckExecutable ret) {
-  var parts = Uri.file(Platform.resolvedExecutable).pathSegments;
-  String basename =  parts[parts.length - 1];
-  var pos = basename.lastIndexOf('.');
-  String result = (pos != -1) ? basename.substring(0, pos) : basename;
-  return ret(result);
+bool checkResolvedExecutable(CheckFunction function) {
+  var uriParts = Uri.file(Platform.resolvedExecutable).pathSegments;
+  String baseName =  uriParts[uriParts.length - 1];
+  var pos = baseName.lastIndexOf('.');
+  String result = (pos != -1) ? baseName.substring(0, pos) : baseName;
+  return function(result);
 }
 
-// Checks that application runs in dart precompiled runtime mode.
-bool get isDartkp => checkMode(((String s) => s == "dart_precompiled_runtime"));
+/// Checks that application runs in dart precompiled runtime mode.
+bool get isDartkp =>
+    checkResolvedExecutable(((String s) => s == "dart_precompiled_runtime"));
 
-// Checks that application runs in AOT mode.
-bool get isAOT => checkMode(((String s) => s != "dart"));
+/// Checks that application runs in AOT mode.
+bool get isAot => checkResolvedExecutable(((String str) => str != "dart"));
diff --git a/Utils/tests/Expect/approxEquals_A01_t01.dart b/Utils/tests/Expect/approxEquals_A01_t01.dart
index 4a7a055..7c6a5a3 100644
--- a/Utils/tests/Expect/approxEquals_A01_t01.dart
+++ b/Utils/tests/Expect/approxEquals_A01_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual,
+///   [num tolerance = null, String reason = ''])
 /// Failure if the difference between expected and actual is greater than the
 /// given tolerance.
 /// @description Checks that no exception is thrown when the difference between
@@ -17,7 +18,8 @@
 main() {
   final double MIN_DOUBLE = Math.pow(2.0, -1074) as double;
   final double NEG_MIN_DOUBLE = -1 * MIN_DOUBLE; 
-  final double MAX_DOUBLE = (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
+  final double MAX_DOUBLE =
+      (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
   final double NEG_MAX_DOUBLE = -1 * MAX_DOUBLE; 
 
   Expect.approxEquals(100.0, 101, 1);
diff --git a/Utils/tests/Expect/approxEquals_A01_t02.dart b/Utils/tests/Expect/approxEquals_A01_t02.dart
index f8d88bc..ac044c7 100644
--- a/Utils/tests/Expect/approxEquals_A01_t02.dart
+++ b/Utils/tests/Expect/approxEquals_A01_t02.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual,
+///   [num tolerance = null, String reason = ''])
 /// Failure if the difference between expected and actual is greater than the
 /// given tolerance.
 /// @description Checks that using arguments with (non-NAN) difference exceeding
@@ -16,7 +17,8 @@
 main() {
   final double MIN_DOUBLE = Math.pow(2.0, -1074) as double;
   final double NEG_MIN_DOUBLE = -1 * MIN_DOUBLE; 
-  final double MAX_DOUBLE = (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
+  final double MAX_DOUBLE =
+      (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
   final double NEG_MAX_DOUBLE = -1 * MAX_DOUBLE; 
 
   check(100.0, 101, 0.1);
@@ -56,7 +58,7 @@
   check(double.negativeInfinity, NEG_MAX_DOUBLE, MAX_DOUBLE, "not empty");
 }
 
-void check(num arg1, num arg2, num tolerance, [String? reason = null]) {
+void check(num arg1, num arg2, num tolerance, [String reason = '']) {
   try {
     Expect.approxEquals(arg1, arg2, tolerance, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/approxEquals_A01_t03.dart b/Utils/tests/Expect/approxEquals_A01_t03.dart
index 6fabc7a..a2ff24c 100644
--- a/Utils/tests/Expect/approxEquals_A01_t03.dart
+++ b/Utils/tests/Expect/approxEquals_A01_t03.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual,
+///   [num tolerance = null, String reason = ''])
 /// Failure if the difference between expected and actual is greater than the
 /// given tolerance.
 /// @description Checks that using negative tolerance (except negative zero) or
@@ -17,7 +18,8 @@
 main() {
   final double MIN_DOUBLE = Math.pow(2.0, -1074) as double;
   final double NEG_MIN_DOUBLE = -1 * MIN_DOUBLE; 
-  final double MAX_DOUBLE = (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
+  final double MAX_DOUBLE =
+      (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
   final double NEG_MAX_DOUBLE = -1 * MAX_DOUBLE; 
 
   check(0, 0, double.negativeInfinity);
@@ -39,7 +41,8 @@
 
   check(double.negativeInfinity, double.negativeInfinity, double.infinity);
   check(double.negativeInfinity, double.negativeInfinity, double.infinity, "");
-  check(double.negativeInfinity, double.negativeInfinity, double.infinity, "not empty");
+  check(double.negativeInfinity, double.negativeInfinity, double.infinity,
+      "not empty");
 
   check(0, double.nan, double.infinity);
   check(0, double.nan, double.infinity, "");
@@ -50,7 +53,7 @@
   check(0, 0, double.nan, "not empty");
 }
 
-void check(num arg1, num arg2, num tolerance, [String? reason = null]) {
+void check(num arg1, num arg2, num tolerance, [String reason = '']) {
   try {
     Expect.approxEquals(arg1, arg2, tolerance, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/approxEquals_A01_t04.dart b/Utils/tests/Expect/approxEquals_A01_t04.dart
index 65cdd0d..30dff7f 100644
--- a/Utils/tests/Expect/approxEquals_A01_t04.dart
+++ b/Utils/tests/Expect/approxEquals_A01_t04.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual,
+///     [num tolerance = null, String reason = null])
 /// Failure if the difference between expected and actual is greater than the
 /// given tolerance.
 /// @description Checks that no exception is thrown when the absolute difference
@@ -18,7 +19,8 @@
 main() {
   final double MIN_DOUBLE = Math.pow(2.0, -1074) as double;
   final double NEG_MIN_DOUBLE = -1 * MIN_DOUBLE; 
-  final double MAX_DOUBLE = (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
+  final double MAX_DOUBLE =
+      (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
   final double NEG_MAX_DOUBLE = -1 * MAX_DOUBLE; 
 
   Expect.approxEquals(100.0, 101, 1.1);
diff --git a/Utils/tests/Expect/approxEquals_A02_t01.dart b/Utils/tests/Expect/approxEquals_A02_t01.dart
index 07e269c..0d35853 100644
--- a/Utils/tests/Expect/approxEquals_A02_t01.dart
+++ b/Utils/tests/Expect/approxEquals_A02_t01.dart
@@ -2,11 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual,
+///   [num tolerance = null, String reason = null])
 /// If no tolerance is given, tolerance is assumed to be the value 4 significant
 /// digits smaller than the value given for expected.
-/// @description Checks that with no tolerance specified, it is indeed assumed to
-/// be 1/10000th of [expected].
+/// @description Checks that with no tolerance specified, it is indeed assumed
+/// to be 1/10000th of [expected].
 /// Zeros and infinities of both signs are tested.
 /// @author rodionov
 
@@ -17,7 +18,8 @@
 main() {
   final double MIN_DOUBLE = Math.pow(2.0, -1074) as double;
   final double NEG_MIN_DOUBLE = -1 * MIN_DOUBLE; 
-  final double MAX_DOUBLE = (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
+  final double MAX_DOUBLE =
+      (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
   final double NEG_MAX_DOUBLE = -1 * MAX_DOUBLE; 
 
   Expect.approxEquals(0, 0);
@@ -59,7 +61,7 @@
   Expect.approxEquals(double.negativeInfinity, 0, null, "not empty");
 }
 
-void check(num arg1, num arg2, [String? reason = null]) {
+void check(num arg1, num arg2, [String reason = '']) {
   try {
     Expect.approxEquals(arg1, arg2, null, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/approxEquals_A03_t01.dart b/Utils/tests/Expect/approxEquals_A03_t01.dart
index 20f0072..2cb6989 100644
--- a/Utils/tests/Expect/approxEquals_A03_t01.dart
+++ b/Utils/tests/Expect/approxEquals_A03_t01.dart
@@ -2,9 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual,
+///     [num tolerance = null, String reason = null])
 /// Passing null as either expected or actual results in Error. 
-/// @description Checks that Error is thrown if any of the required arguments are null.
+/// @description Checks that Error is thrown if any of the required arguments
+/// are null.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -35,7 +37,7 @@
   check(null, null, 0, "not empty");
 }
 
-void check(num? arg1, num? arg2, [num? tolerance = null, String? reason = null]) {
+void check(num? arg1, num? arg2, [num? tolerance = null, String reason = '']) {
   try {
     Expect.approxEquals(arg1 as num, arg2 as num, tolerance, reason);
     Expect.fail("Error expected");
diff --git a/Utils/tests/Expect/approxEquals_A04_t01.dart b/Utils/tests/Expect/approxEquals_A04_t01.dart
index 47bf7fa..4b60173 100644
--- a/Utils/tests/Expect/approxEquals_A04_t01.dart
+++ b/Utils/tests/Expect/approxEquals_A04_t01.dart
@@ -2,9 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void approxEquals(num expected, num actual, [num tolerance = null, String reason = null])
+/// @assertion static void approxEquals(num expected, num actual, [
+///   num tolerance = null, String reason = null])
 /// Descriptive error message is provided in case of failure.
-/// @description Checks that message of thrown ExpectException includes 
+///
+/// @description Checks that message of thrown [ExpectException] includes
 /// representation of the expected, actual and tolerance values, as well as the
 /// reason.
 /// @author varlax
@@ -16,7 +18,8 @@
 main() {
   final double MIN_DOUBLE = Math.pow(2.0, -1074) as double;
   final double NEG_MIN_DOUBLE = -1 * MIN_DOUBLE; 
-  final double MAX_DOUBLE = (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
+  final double MAX_DOUBLE =
+      (2 - Math.pow(2.0, -52)) * Math.pow(2.0, 1023) as double;
   final double NEG_MAX_DOUBLE = -1 * MAX_DOUBLE; 
 
   // min double > 0 / 10000
@@ -36,7 +39,7 @@
   check(0, -0.0, double.nan, "");
 }
 
-void check(num arg1, num arg2, [num? tol = null, String? reason = null]) {
+void check(num arg1, num arg2, [num? tol = null, String reason = '']) {
   try {
     Expect.approxEquals(arg1, arg2, tol, reason);
     throw new Exception("ExpectException expected");
@@ -45,10 +48,8 @@
     String msg = e.message as String;
     if (!msg.contains(arg1.toString(), 0)) throw "no expected value";
     if (!msg.contains(arg2.toString(), 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
-    if (tol == null) {
-      tol = (arg1 / Math.pow(10.0, 4.0)).abs();
-    }
+    if (!reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    tol ??= (arg1 / Math.pow(10.0, 4.0)).abs();
     if (!msg.contains(tol.toString(), 0)) throw "no tolerance";
   }
 }
diff --git a/Utils/tests/Expect/equals_A01_t01.dart b/Utils/tests/Expect/equals_A01_t01.dart
index b27e0ae..0dcd839 100644
--- a/Utils/tests/Expect/equals_A01_t01.dart
+++ b/Utils/tests/Expect/equals_A01_t01.dart
@@ -2,11 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void equals(var expected, var actual, [String reason = null])
+/// @assertion static void equals(var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are equal (using [:==:]).
-/// @description Checks that no exception is thrown when the arguments are equal,
-/// regardless of reason (the last argument). Null, numeric and Object values are
-/// tested.
+///
+/// @description Checks that no exception is thrown when the arguments are
+/// equal, regardless of reason (the last argument). Null, numeric and [Object]
+/// values are tested.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
diff --git a/Utils/tests/Expect/equals_A01_t02.dart b/Utils/tests/Expect/equals_A01_t02.dart
index 4d56b0a..fe487f7 100644
--- a/Utils/tests/Expect/equals_A01_t02.dart
+++ b/Utils/tests/Expect/equals_A01_t02.dart
@@ -2,11 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void equals(var expected, var actual, [String reason = null])
+/// @assertion static void equals(var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are equal (using [:==:]).
-/// @description Checks that using non-equal arguments results in ExpectException
-///              being thrown. Arguments being tested include null, boolean, numeric and
-///              Object, along with null, empty and non-empty reason arguments.
+///
+/// @description Checks that using non-equal arguments results in
+/// [ExpectException] being thrown. Arguments being tested include null,
+/// boolean, numeric and [Object], along with empty and non-empty reason
+/// arguments.
+///
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -27,7 +30,7 @@
   check(null, false);
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.equals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/equals_A01_t03.dart b/Utils/tests/Expect/equals_A01_t03.dart
index c0af4b3..7b7dc22 100644
--- a/Utils/tests/Expect/equals_A01_t03.dart
+++ b/Utils/tests/Expect/equals_A01_t03.dart
@@ -2,9 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void equals(var expected, var actual, [String reason = null])
+/// @assertion static void equals(var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are equal (using [:==:]).
-/// @description Checks that object equality is checked with == operator (on expected value).
+///
+/// @description Checks that object equality is checked with == operator (on
+/// expected value).
+///
 /// @author varlax
 
 import "../../../Utils/expect.dart";
diff --git a/Utils/tests/Expect/equals_A01_t04.dart b/Utils/tests/Expect/equals_A01_t04.dart
index 4eacf71..3c81ff9 100644
--- a/Utils/tests/Expect/equals_A01_t04.dart
+++ b/Utils/tests/Expect/equals_A01_t04.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void equals(var expected, var actual, [String reason = null])
+/// @assertion static void equals(var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are equal (using [:==:]).
 /// @description NaNs considered equals
 /// @author varlax
diff --git a/Utils/tests/Expect/equals_A02_t01.dart b/Utils/tests/Expect/equals_A02_t01.dart
index b70721a..c22859d 100644
--- a/Utils/tests/Expect/equals_A02_t01.dart
+++ b/Utils/tests/Expect/equals_A02_t01.dart
@@ -2,9 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void equals(var expected, var actual, [String reason = null])
+/// @assertion static void equals(var expected, var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
-/// @description Checks that message of thrown ExpectException includes 
+/// @description Checks that message of thrown [ExpectException] includes
 /// representation of the expected and actual values, as well as the reason.
 /// @author varlax
 
@@ -26,15 +26,18 @@
   check(null, false);
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.equals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     if (e.message == null) throw "Exception message is empty";
     String msg = e.message as String;
-    if (!msg.contains(arg1 != null ? arg1.toString() : "null", 0)) throw "no expected value";
-    if (!msg.contains(arg2 != null ? arg2.toString() : "null", 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (!msg.contains(arg1 != null ? arg1.toString() : "null", 0))
+      throw "no expected value";
+    if (!msg.contains(arg2 != null ? arg2.toString() : "null", 0))
+      throw "no actual value";
+    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
+      throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/fail_A01_t01.dart b/Utils/tests/Expect/fail_A01_t01.dart
index a5ecb21..94ae214 100644
--- a/Utils/tests/Expect/fail_A01_t01.dart
+++ b/Utils/tests/Expect/fail_A01_t01.dart
@@ -4,24 +4,23 @@
 
 /// @assertion static void fail(String msg)
 /// Unconditional failure. 
-/// @description Checks that this method always results in failure, regardless of
-/// whether or not the argument is null or empty.
+/// @description Checks that this method always results in failure, regardless
+/// of whether or not the argument is empty.
 /// @author rodionov
 /// @needsreview The exact mechanism of signaling failure is not documented. We
 /// know it's ExpectException, though.
 
-import "../../../Utils/expect.dart";
+import '../../../Utils/expect.dart';
 
 main() {
-  check(null);
-  check("");
-  check("sdjgksjdg");
+  check('');
+  check('sdjgksjdg');
 }
 
-void check(String? msg) {
+void check(String msg) {
   try {
     Expect.fail(msg);
-    throw new Exception("ExpectException expected");
+    throw new Exception('ExpectException expected');
   } on ExpectException catch(e) {
   }
 }
diff --git a/Utils/tests/Expect/fail_A02_t01.dart b/Utils/tests/Expect/fail_A02_t01.dart
index af24574..aa8856b 100644
--- a/Utils/tests/Expect/fail_A02_t01.dart
+++ b/Utils/tests/Expect/fail_A02_t01.dart
@@ -4,24 +4,25 @@
 
 /// @assertion static void fail(String msg)
 /// Descriptive error message is provided. 
-/// @description Checks that message of thrown ExpectException is set to the msg argument.
+/// @description Checks that message of thrown ExpectException is set to the msg
+/// argument.
 /// @author varlax
 
 import "../../../Utils/expect.dart";
 
 main() {
-  check(null);
   check("");
   check("sdjgksjdg");
 }
 
-void check(String? msg) {
+void check(String msg) {
   try {
     Expect.fail(msg);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String res = e.message as String;
-    if (!res.contains(msg.toString(), 0)) throw "ExpectException message: '${res}'"
-      " doesn't contain the argument of fail() ( ${ msg.toString()} )";
+    if (!res.contains(msg.toString(), 0))
+      throw "ExpectException message: '${res}'"
+        " doesn't contain the argument of fail() ( ${ msg.toString()} )";
   }
 }
diff --git a/Utils/tests/Expect/identical_A01_t01.dart b/Utils/tests/Expect/identical_A01_t01.dart
index 8521b56..5401ad9 100644
--- a/Utils/tests/Expect/identical_A01_t01.dart
+++ b/Utils/tests/Expect/identical_A01_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void identical(var expected, var actual, [String reason = null]) 
+/// @assertion static void identical(
+///    var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are identical.
 /// @description Checks that no exception is thrown when the arguments are
 /// identical, regardless of reason (the last argument). Null, numeric, String
diff --git a/Utils/tests/Expect/identical_A01_t02.dart b/Utils/tests/Expect/identical_A01_t02.dart
index e6905c7..6bc54fb 100644
--- a/Utils/tests/Expect/identical_A01_t02.dart
+++ b/Utils/tests/Expect/identical_A01_t02.dart
@@ -2,12 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void identical(var expected, var actual, [String reason = null]) 
+/// @assertion static void identical(
+///   var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are identical.
 /// @description Checks that using non-identical arguments results in
 /// [ExpectException] being thrown. Arguments being tested include null, boolean,
-/// String, numeric and Object, along with null, empty and non-empty reason
-/// arguments.
+/// String, numeric and Object, along with empty and non-empty reason arguments.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -42,7 +42,7 @@
   check(new Object(), new Object(), "not empty");
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.identical(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/identical_A01_t03.dart b/Utils/tests/Expect/identical_A01_t03.dart
index 08a1546..13a540e 100644
--- a/Utils/tests/Expect/identical_A01_t03.dart
+++ b/Utils/tests/Expect/identical_A01_t03.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void identical(var expected, var actual, [String reason = null]) 
+/// @assertion static void identical(
+///     var expected, var actual, [String reason = ''])
 /// Checks whether the expected and actual values are identical.
 /// @description Checks that equality operator is not used.
 /// @author varlax
@@ -15,10 +16,9 @@
   }
 }
 
-
 main() {
   try {
-    Expect.identical(new A(), new A());
+    Expect.identical(A(), A());
     throw "ExpectException expected";
   } on ExpectException catch(ok) {
   }
diff --git a/Utils/tests/Expect/identical_A02_t01.dart b/Utils/tests/Expect/identical_A02_t01.dart
index 7b65c63..01823b7 100644
--- a/Utils/tests/Expect/identical_A02_t01.dart
+++ b/Utils/tests/Expect/identical_A02_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void identical(var expected, var actual, [String reason = null]) 
+/// @assertion static void identical(
+///   var expected, var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
 /// @description Checks that message of thrown ExpectException includes 
 /// representation of the expected and actual values, as well as the reason.
@@ -40,14 +41,17 @@
   check(new Object(), new Object(), "not empty");
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.identical(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String msg = e.message as String;
-    if (!msg.contains(arg1 != null ? arg1.toString() : "null", 0)) throw "no expected value";
-    if (!msg.contains(arg2 != null ? arg2.toString() : "null", 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (!msg.contains(arg1 != null ? arg1.toString() : "null", 0))
+      throw "no expected value";
+    if (!msg.contains(arg2 != null ? arg2.toString() : "null", 0))
+      throw "no actual value";
+    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
+      throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/isFalse_A01_t01.dart b/Utils/tests/Expect/isFalse_A01_t01.dart
index 8d6387d..a71cb93 100644
--- a/Utils/tests/Expect/isFalse_A01_t01.dart
+++ b/Utils/tests/Expect/isFalse_A01_t01.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isFalse(var actual, [String reason = null])
+/// @assertion static void isFalse(var actual, [String reason = ''])
 /// Checks whether the actual value is a bool and its value is false. 
 /// @description Checks that no exception is thrown when the argument is a bool
 /// and its value is false, regardless of reason (the last argument).
diff --git a/Utils/tests/Expect/isFalse_A01_t02.dart b/Utils/tests/Expect/isFalse_A01_t02.dart
index 97c0b5c..6d8e74e 100644
--- a/Utils/tests/Expect/isFalse_A01_t02.dart
+++ b/Utils/tests/Expect/isFalse_A01_t02.dart
@@ -2,11 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isFalse(var actual, [String reason = null]) 
+/// @assertion static void isFalse(var actual, [String reason = ''])
 /// Checks whether the actual value is a bool and its value is false.
 /// @description Checks that using non-boolean argument or boolean true results
-/// in ExpectException being thrown. Arguments being tested include null, numeric
-/// and Object, along with null, empty and non-empty reason arguments.
+/// in [ExpectException] being thrown. Arguments being tested include null,
+/// numeric and [Object], along with empty and non-empty reason arguments.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -29,7 +29,7 @@
   check(new Object(), "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isFalse(arg, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/isFalse_A02_t01.dart b/Utils/tests/Expect/isFalse_A02_t01.dart
index 017b943..9193f38 100644
--- a/Utils/tests/Expect/isFalse_A02_t01.dart
+++ b/Utils/tests/Expect/isFalse_A02_t01.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isFalse(var actual, [String reason = null]) 
+/// @assertion static void isFalse(var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
 /// @description Checks that message of thrown ExpectException includes 
 /// representation of the actual value, as well as the reason.
@@ -28,7 +28,7 @@
   check(new Object(), "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isFalse(arg, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/isNotNull_A01_t01.dart b/Utils/tests/Expect/isNotNull_A01_t01.dart
index 059b9b2..7a2edb9 100644
--- a/Utils/tests/Expect/isNotNull_A01_t01.dart
+++ b/Utils/tests/Expect/isNotNull_A01_t01.dart
@@ -2,10 +2,10 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isNotNull(var actual, [String reason = null])
+/// @assertion static void isNotNull(var actual, [String reason = ''])
 /// Checks whether [actual] is not null.
-/// @description Checks that no exception is thrown when the argument is not null,
-/// regardless of reason (the last argument). Boolean, numeric and Object
+/// @description Checks that no exception is thrown when the argument is not
+/// null, regardless of reason (the last argument). Boolean, numeric and Object
 /// arguments are used.
 /// @author rodionov
 
diff --git a/Utils/tests/Expect/isNotNull_A01_t02.dart b/Utils/tests/Expect/isNotNull_A01_t02.dart
index 6b9f0d1..61e9983 100644
--- a/Utils/tests/Expect/isNotNull_A01_t02.dart
+++ b/Utils/tests/Expect/isNotNull_A01_t02.dart
@@ -5,7 +5,7 @@
 /// @assertion static void isNotNull(var actual, [String reason = null])
 /// Checks whether [actual] is not null.
 /// @description Checks that using a null argument results in ExpectException
-/// being thrown, regardless of whether the reason (2nd argument) is null.
+/// being thrown, regardless of whether the reason (2nd argument) is empty.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -16,7 +16,7 @@
   check(null, "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isNotNull(arg, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/isNotNull_A02_t01.dart b/Utils/tests/Expect/isNotNull_A02_t01.dart
index ad53c0b..2c6e51d 100644
--- a/Utils/tests/Expect/isNotNull_A02_t01.dart
+++ b/Utils/tests/Expect/isNotNull_A02_t01.dart
@@ -2,9 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isNotNull(var actual, [String reason = null])
+/// @assertion static void isNotNull(var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
-/// @description Checks that message of thrown ExpectException includes 
+/// @description Checks that message of thrown [ExpectException] includes
 /// representation of the actual value, as well as the reason.
 /// @author varlax
 
@@ -16,13 +16,14 @@
   check(null, "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isNotNull(arg, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String msg = e.message as String;
     if (!msg.contains("null", 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
+      throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/isNull_A01_t01.dart b/Utils/tests/Expect/isNull_A01_t01.dart
index 013f8fd..d3b56e9 100644
--- a/Utils/tests/Expect/isNull_A01_t01.dart
+++ b/Utils/tests/Expect/isNull_A01_t01.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isNull(var actual, [String reason = null])
+/// @assertion static void isNull(var actual, [String reason = ''])
 /// Checks whether [actual] is null.
 /// @description Checks that no exception is thrown when the argument is null,
 /// regardless of reason (the last argument).
diff --git a/Utils/tests/Expect/isNull_A01_t02.dart b/Utils/tests/Expect/isNull_A01_t02.dart
index 94e4e55..51e8088 100644
--- a/Utils/tests/Expect/isNull_A01_t02.dart
+++ b/Utils/tests/Expect/isNull_A01_t02.dart
@@ -2,11 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isNull(var actual, [String reason = null])
+/// @assertion static void isNull(var actual, [String reason = ''])
 /// Checks whether [actual] is null.
-/// @description Checks that using non-null argument results in ExpectException
-/// being thrown. Arguments being tested include boolean, numeric and Object,
-/// along with null, empty and non-empty reason arguments.
+/// @description Checks that using non-null argument results in
+/// [ExpectException] being thrown. Arguments being tested include boolean,
+/// numeric and [Object], along with empty and non-empty reason arguments.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -29,7 +29,7 @@
   check(new Object(), "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isNull(arg, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/isNull_A02_t01.dart b/Utils/tests/Expect/isNull_A02_t01.dart
index cc74e23..a0f62e0 100644
--- a/Utils/tests/Expect/isNull_A02_t01.dart
+++ b/Utils/tests/Expect/isNull_A02_t01.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isNull(var actual, [String reason = null])
+/// @assertion static void isNull(var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
 /// @description Checks that message of thrown ExpectException includes 
 /// representation of the actual value, as well as the reason.
@@ -28,13 +28,14 @@
   check(new Object(), "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isNull(arg, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String msg = e.message as String;
     if (!msg.contains(arg.toString(), 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
+      throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/isTrue_A01_t02.dart b/Utils/tests/Expect/isTrue_A01_t02.dart
index 37768f6..838d1d8 100644
--- a/Utils/tests/Expect/isTrue_A01_t02.dart
+++ b/Utils/tests/Expect/isTrue_A01_t02.dart
@@ -2,11 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isTrue(var actual, [String reason = null])
+/// @assertion static void isTrue(var actual, [String reason = ''])
 /// Checks whether the actual value is a bool and its value is true.
 /// @description Checks that using non-boolean argument or boolean false results
 /// in ExpectException being thrown. Arguments being tested include null,
-/// numeric and Object, along with null, empty and non-empty reason arguments.
+/// numeric and Object, along with empty and non-empty reason arguments.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -29,7 +29,7 @@
   check(new Object(), "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isTrue(arg, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/isTrue_A02_t01.dart b/Utils/tests/Expect/isTrue_A02_t01.dart
index 3d6fa8c..b325cf1 100644
--- a/Utils/tests/Expect/isTrue_A02_t01.dart
+++ b/Utils/tests/Expect/isTrue_A02_t01.dart
@@ -2,9 +2,9 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void isTrue(var actual, [String reason = null])
+/// @assertion static void isTrue(var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
-/// @description Checks that message of thrown ExpectException includes 
+/// @description Checks that message of thrown [ExpectException] includes
 /// representation of the actual value, as well as the reason.
 /// @author varlax
 
@@ -28,13 +28,15 @@
   check(new Object(), "not empty");
 }
 
-void check(var arg, [String? reason = null]) {
+void check(var arg, [String reason = '']) {
   try {
     Expect.isTrue(arg, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String msg = e.message as String;
-    if (!msg.contains(arg != null ? arg.toString() : "null", 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (!msg.contains(arg != null ? arg.toString() : "null", 0))
+      throw "no actual value";
+    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
+      throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/listEquals_A01_t01.dart b/Utils/tests/Expect/listEquals_A01_t01.dart
index c9f1eac..3e76fff 100644
--- a/Utils/tests/Expect/listEquals_A01_t01.dart
+++ b/Utils/tests/Expect/listEquals_A01_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void listEquals(List expected, List actual, [String reason = null])
+/// @assertion static void listEquals(
+///   List expected, List actual, [String reason = ''])
 /// Checks that all elements in [expected] and [actual] are equal [:==:].
 /// @description Checks that no exception is thrown when the compared lists have
 /// equal contents, regardless of reason (the last argument).
diff --git a/Utils/tests/Expect/listEquals_A01_t02.dart b/Utils/tests/Expect/listEquals_A01_t02.dart
index 5116f13..bedcca8 100644
--- a/Utils/tests/Expect/listEquals_A01_t02.dart
+++ b/Utils/tests/Expect/listEquals_A01_t02.dart
@@ -2,10 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void listEquals(List expected, List actual, [String reason = null])
+/// @assertion static void listEquals(
+///   List expected, List actual, [String reason = ''])
 /// Checks that all elements in [expected] and [actual] are equal [:==:].
 /// @description Checks that using list with non-equal contents results in
-/// ExpectException being thrown.
+/// [ExpectException] being thrown.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -31,7 +32,7 @@
   check([0,1,2,3],[1,2,3]);
 }
 
-void check(List arg1, List arg2, [String? reason = null]) {
+void check(List arg1, List arg2, [String reason = '']) {
   try {
     Expect.listEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/listEquals_A01_t03.dart b/Utils/tests/Expect/listEquals_A01_t03.dart
index 9ca72a4..a3d393e 100644
--- a/Utils/tests/Expect/listEquals_A01_t03.dart
+++ b/Utils/tests/Expect/listEquals_A01_t03.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void listEquals(List expected, List actual, [String reason = null])
+/// @assertion static void listEquals(
+///   List expected, List actual, [String reason = ''])
 /// Checks that all elements in [expected] and [actual] are equal [:==:].
 /// @description Checks that operator == on elements is used for checking.
 /// @author varlax
diff --git a/Utils/tests/Expect/listEquals_A02_t01.dart b/Utils/tests/Expect/listEquals_A02_t01.dart
index ffe8fae..bed50f8 100644
--- a/Utils/tests/Expect/listEquals_A02_t01.dart
+++ b/Utils/tests/Expect/listEquals_A02_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void listEquals(List expected, List actual, [String reason = null])
+/// @assertion static void listEquals(
+///   List expected, List actual, [String reason = ''])
 /// Passing null as either expected or actual results in ExpectException. 
 /// @description Checks that ExpectException is thrown if any of the required
 /// arguments are null.
@@ -24,7 +25,7 @@
   check(null, null, "not empty");
 }
 
-void check(List? arg1, List? arg2, [String? reason = null]) {
+void check(List? arg1, List? arg2, [String reason = '']) {
   try {
     Expect.listEquals(arg1, arg2, reason);
     Expect.fail("Error expected");
diff --git a/Utils/tests/Expect/listEquals_A03_t01.dart b/Utils/tests/Expect/listEquals_A03_t01.dart
index 171b69e..db55f26 100644
--- a/Utils/tests/Expect/listEquals_A03_t01.dart
+++ b/Utils/tests/Expect/listEquals_A03_t01.dart
@@ -2,10 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void listEquals(List expected, List actual, [String reason = null])
+/// @assertion static void listEquals(
+///   List expected, List actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
-/// @description Checks that message of thrown ExpectException includes 
-/// representation of the expected and mismatched elements, as well as the reason.
+/// @description Checks that message of thrown [ExpectException] includes
+/// representation of the expected and mismatched elements, as well as the
+/// reason.
 /// @author varlax
 
 import "../../../Utils/expect.dart";
@@ -29,21 +31,22 @@
   check([1,2,3], [1,2,3,4]);
   check([0,1,2,3], [1,2,3], "235dsf435g gret sd");
 
-  check([1, 5, 3], [1, 10, 3], null, 1);
+  check([1, 5, 3], [1, 10, 3], '', 1);
 }
 
-void check(List arg1, List arg2, [String? reason = null, int index = 0]) {
+void check(List arg1, List arg2, [String reason = '', int index = 0]) {
   try {
     Expect.listEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
-//  } on Error catch(e) {
     String msg = e.message as String;
     if(arg1.length != arg2.length) {
-      if(!msg.contains(arg1.length.toString(), 0) && !msg.contains(arg2.length.toString(), 0)) {
+      if(!msg.contains(arg1.length.toString(), 0)
+            && !msg.contains(arg2.length.toString(), 0)) {
         throw "exception message ( ${msg} ) doesn't mention list lengths";
       }
-      if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+      if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
+        throw "no reason";
     } else {
       var a1 = arg1[index], a2 = arg2[index];
       String a1str = a1 != null ? a1.toString() : "null", 
@@ -51,16 +54,17 @@
 
 // TODO improve Expect.listEquals to inform index of the first mismatch
 //      if (!msg.contains('$index', 0))
-//        throw "exception message: ( ${msg} ) doesn't mention the index of first mismatch ($index)";
+//        throw "exception message: ( ${msg} ) doesn't mention the index of "
+//             "first mismatch ($index)";
       
-      if (!msg.contains(a1str, 0))
-        throw "exception message: ( ${msg} ) doesn't mention the expected value ($a1str)";
+      if (!msg.contains(a1str, 0)) throw "exception message: ( ${msg} ) "
+          "doesn't mention the expected value ($a1str)";
           
-      if (!msg.contains(a2str, 0))
-        throw "exception message: ( ${msg} ) doesn't mention the actual value ($a2str)";
+      if (!msg.contains(a2str, 0)) throw "exception message: ( ${msg} ) "
+          "doesn't mention the actual value ($a2str)";
       
-      if (reason != null && !reason.isEmpty && !msg.contains(reason, 0))
-        "exception message: ( ${msg} ) doesn't mention the specified reason ($reason)";
+      if (!reason.isEmpty && !msg.contains(reason, 0)) throw "exception "
+          "message: ( ${msg} ) doesn't mention the specified reason ($reason)";
     }
   }
 }
diff --git a/Utils/tests/Expect/notEquals_A01_t01.dart b/Utils/tests/Expect/notEquals_A01_t01.dart
index 04172b3..8f5580f 100644
--- a/Utils/tests/Expect/notEquals_A01_t01.dart
+++ b/Utils/tests/Expect/notEquals_A01_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void notEquals(var unexpected, var actual, [String reason = null])
+/// @assertion static void notEquals(
+///   var unexpected, var actual, [String reason = ''])
 /// Checks whether the unexpected and actual values are not equal (using [:!=:]).
 /// @description Checks that no exception is thrown when the arguments are not
 /// equal, regardless of reason (the last argument). Null, numeric and Object
diff --git a/Utils/tests/Expect/notEquals_A01_t02.dart b/Utils/tests/Expect/notEquals_A01_t02.dart
index 3e74033..afb6bab 100644
--- a/Utils/tests/Expect/notEquals_A01_t02.dart
+++ b/Utils/tests/Expect/notEquals_A01_t02.dart
@@ -2,11 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void notEquals(var unexpected, var actual, [String reason = null])
+/// @assertion static void notEquals(
+///   var unexpected, var actual, [String reason = ''])
 /// Checks whether the unexpected and actual values are not equal (using [:!=:]).
 /// @description Checks that using equal arguments results in ExpectException
 /// being thrown. Arguments being tested include boolean, numeric and Object,
-/// along with null, empty and non-empty reason arguments.
+/// along with empty and non-empty reason arguments.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -32,7 +33,7 @@
   check("", "", "bla");
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.notEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/notEquals_A01_t03.dart b/Utils/tests/Expect/notEquals_A01_t03.dart
index fcc1e3c..77292e1 100644
--- a/Utils/tests/Expect/notEquals_A01_t03.dart
+++ b/Utils/tests/Expect/notEquals_A01_t03.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void notEquals(var unexpected, var actual, [String reason = null])
+/// @assertion static void notEquals(
+///   var unexpected, var actual, [String reason = ''])
 /// Checks whether the unexpected and actual values are not equal (using [:!=:]).
 /// @description Checks that object equality is checked with == operator (on
 /// unexpected value).
diff --git a/Utils/tests/Expect/notEquals_A02_t01.dart b/Utils/tests/Expect/notEquals_A02_t01.dart
index cff336b..83660f4 100644
--- a/Utils/tests/Expect/notEquals_A02_t01.dart
+++ b/Utils/tests/Expect/notEquals_A02_t01.dart
@@ -2,7 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void notEquals(var unexpected, var actual, [String reason = null])
+/// @assertion static void notEquals(var unexpected, var actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
 /// @description Checks that message of thrown ExpectException includes 
 /// representation of the unexpected and actual values, as well as the reason.
@@ -31,14 +31,16 @@
   check("", "", "bla");
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.notEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String msg = e.message as String;
-    if (!msg.contains(arg1 != null ? arg1.toString() : "null", 0)) throw "no unexpected value";
-    if (!msg.contains(arg2 != null ? arg2.toString() : "null", 0)) throw "no actual value";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (!msg.contains(arg1 != null ? arg1.toString() : "null", 0))
+      throw "no unexpected value";
+    if (!msg.contains(arg2 != null ? arg2.toString() : "null", 0))
+      throw "no actual value";
+    if (!reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/setEquals_A01_t01.dart b/Utils/tests/Expect/setEquals_A01_t01.dart
index df29145..ed67ca2 100644
--- a/Utils/tests/Expect/setEquals_A01_t01.dart
+++ b/Utils/tests/Expect/setEquals_A01_t01.dart
@@ -2,11 +2,13 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void setEquals(Iterable expected, Iterable actual, [String reason = null])
+/// @assertion static void setEquals(
+///     Iterable expected, Iterable actual, [String reason = ''])
 /// Checks that every element of [expected] is also in [actual], and that every
 /// element of [actual] is also in [expected].
 /// @description Checks that no exception is thrown when the compared Iterables
-/// have equal contents, regardless of their order and reason (the last argument).
+/// have equal contents, regardless of their order and reason (the last
+/// argument).
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
diff --git a/Utils/tests/Expect/setEquals_A01_t02.dart b/Utils/tests/Expect/setEquals_A01_t02.dart
index ac968a8..847c45f 100644
--- a/Utils/tests/Expect/setEquals_A01_t02.dart
+++ b/Utils/tests/Expect/setEquals_A01_t02.dart
@@ -2,11 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void setEquals(Iterable expected, Iterable actual, [String reason = null])
+/// @assertion static void setEquals(
+///   Iterable expected, Iterable actual, [String reason = ''])
 /// Checks that every element of [expected] is also in [actual], and that every
 /// element of [actual] is also in [expected].
 /// @description Checks that using Iterables with non-equal contents results in
-/// ExpectException being thrown.
+/// [ExpectException] being thrown.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -33,7 +34,7 @@
   }
 }
 
-void check(Iterable arg1, Iterable arg2, [String? reason = null]) {
+void check(Iterable arg1, Iterable arg2, [String reason = '']) {
   try {
     Expect.setEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/setEquals_A02_t01.dart b/Utils/tests/Expect/setEquals_A02_t01.dart
index eed9030..5a085af 100644
--- a/Utils/tests/Expect/setEquals_A02_t01.dart
+++ b/Utils/tests/Expect/setEquals_A02_t01.dart
@@ -2,10 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void setEquals(Iterable expected, Iterable actual, [String reason = null])
-/// Passing null as either expected or actual results in Error. 
-/// @description Checks that Error is thrown if any of the required arguments are
-/// null.
+/// @assertion static void setEquals(
+///   Iterable expected, Iterable actual, [String reason = ''])
+/// Passing null as either expected or actual results in [Error].
+/// @description Checks that Error is thrown if any of the required arguments
+/// are null.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -24,7 +25,7 @@
   check(null, null, "not empty");
 }
 
-void check(var arg1, var arg2, [String ?reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.setEquals(arg1, arg2, reason);
     Expect.fail("Error expected");
diff --git a/Utils/tests/Expect/setEquals_A03_t01.dart b/Utils/tests/Expect/setEquals_A03_t01.dart
index d188ad7..66ce433 100644
--- a/Utils/tests/Expect/setEquals_A03_t01.dart
+++ b/Utils/tests/Expect/setEquals_A03_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void setEquals(Iterable expected, Iterable actual, [String reason = null])
+/// @assertion static void setEquals(
+///   Iterable expected, Iterable actual, [String reason = ''])
 /// Descriptive error message is provided in case of failure.
 /// @description Checks that message of thrown ExpectException includes 
 /// representation of extra and missing elements, as well as the reason.
@@ -17,20 +18,29 @@
       [1, 2]
       );
   
-  check([1,2,3],[2,3],[1], "blah sdsder rt3 4");
-  check([234,456,777],[92374,3425,"assa"], [234,456,777,92374,3425,"assa"], "4 4 44  45  45 2__");
-  
+  check(
+      [1,2,3],
+      [2,3],
+      [1],
+      "blah sdsder rt3 4");
+
+  check(
+      [234,456,777],
+      [92374,3425,"assa"],
+      [234,456,777,92374,3425,"assa"],
+      "4 4 44  45  45 2__");
 }
 
-void check(Iterable arg1, Iterable arg2, Iterable arg3, [String? reason = null]) {
+void check(Iterable arg1, Iterable arg2, Iterable arg3, [String reason = '']) {
   try {
     Expect.setEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
   } on ExpectException catch(e) {
     String msg = e.message as String;
     for (var el in arg3) {
-      if (!msg.contains(el != null ? el.toString() : "null", 0)) throw "no element $el";
+      if (!msg.contains(el != null ? el.toString() : "null", 0))
+        throw "no element $el";
     }
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (!reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/stringEquals_A01_t01.dart b/Utils/tests/Expect/stringEquals_A01_t01.dart
index bf88934..940deb5 100644
--- a/Utils/tests/Expect/stringEquals_A01_t01.dart
+++ b/Utils/tests/Expect/stringEquals_A01_t01.dart
@@ -2,11 +2,12 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void stringEquals(String expected, String actual, [String reason = null])
+/// @assertion static void stringEquals(
+///   String expected, String actual, [String reason = ''])
 /// Specialized equality test for strings. 
-/// @description Checks that no exception is thrown when the string arguments are
-/// equal (including the case when they're null), regardless of reason (the last
-/// argument). Null, numeric and Object values are tested.
+/// @description Checks that no exception is thrown when the string arguments
+/// are equal (including the case when they're null), regardless of reason (the
+/// last argument). Null, numeric and Object values are tested.
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
diff --git a/Utils/tests/Expect/stringEquals_A01_t02.dart b/Utils/tests/Expect/stringEquals_A01_t02.dart
index 3e299e6..5feff5b 100644
--- a/Utils/tests/Expect/stringEquals_A01_t02.dart
+++ b/Utils/tests/Expect/stringEquals_A01_t02.dart
@@ -2,10 +2,11 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void stringEquals(String expected, String actual, [String reason = null])
+/// @assertion static void stringEquals(
+///   String expected, String actual, [String reason = ''])
 /// Specialized equality test for strings. 
 /// @description Checks that using non-equal string arguments results in
-/// ExpectException being thrown, regardless of reason (the last argument).
+/// [ExpectException] being thrown, regardless of reason (the last argument).
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -26,7 +27,7 @@
   check("1", "1.0");
 }
 
-void check(var arg1, var arg2, [String? reason = null]) {
+void check(var arg1, var arg2, [String reason = '']) {
   try {
     Expect.stringEquals(arg1, arg2, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/stringEquals_A02_t01.dart b/Utils/tests/Expect/stringEquals_A02_t01.dart
index 403ecb5..cad3ac2 100644
--- a/Utils/tests/Expect/stringEquals_A02_t01.dart
+++ b/Utils/tests/Expect/stringEquals_A02_t01.dart
@@ -2,7 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void stringEquals(String expected, String actual, [String reason = null])
+/// @assertion static void stringEquals(
+///   String expected, String actual, [String reason = ''])
 /// When the strings don't match,
 /// this method shows where the mismatch starts and ends. 
 /// @description Checks that message of thrown ExpectException includes 
@@ -22,7 +23,7 @@
   check("", null, "null", null, "not empty");
 }
 
-void check(var exp, var act, var arg1, [var arg2 = null, String? reason = null]) {
+void check(var exp, var act, var arg1, [var arg2 = null, String reason = '']) {
   try {
     Expect.stringEquals(exp, act, reason);
     throw new Exception("ExpectException expected");
@@ -32,6 +33,6 @@
     if (!msg.contains(act.toString(), 0)) throw "no actual value";
     if (arg1 != null && !msg.contains(arg1, 0)) throw "no correct diff";
     if (arg2 != null && !msg.contains(arg2, 0)) throw "no correct diff";
-    if (reason != null && !reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
+    if (!reason.isEmpty && !msg.contains(reason, 0)) throw "no reason";
   }
 }
diff --git a/Utils/tests/Expect/throws_A01_t01.dart b/Utils/tests/Expect/throws_A01_t01.dart
index 44938ca..6919d86 100644
--- a/Utils/tests/Expect/throws_A01_t01.dart
+++ b/Utils/tests/Expect/throws_A01_t01.dart
@@ -2,14 +2,17 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void throws(void f(), [_CheckExceptionFn check = null, String reason = null])
+/// @assertion static void throws(
+///   void f(), [_CheckExceptionFn check = null, String reason = ''])
 /// typedef bool _CheckExceptionFn(exception)
 /// Calls the function [f] and verifies that it throws an exception.
 /// The optional [check] function can provide additional validation that the
 /// correct exception is being thrown.
+///
 /// @description Checks that if the tested method doesn't throw an exception,
 /// this method fails regardless of whether the validating function is null,
 /// returns true or false and whether the reason is null.
+///
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -34,7 +37,7 @@
   check(badboy, (e) => false, "not empty");
 }
 
-void check(void f(), [checkFn? ch = null, String? reason = null]) {
+void check(void f(), [checkFn? ch = null, String reason = '']) {
   try {
     Expect.throws(f, ch, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/throws_A01_t02.dart b/Utils/tests/Expect/throws_A01_t02.dart
index 6a99b0b..189947d 100644
--- a/Utils/tests/Expect/throws_A01_t02.dart
+++ b/Utils/tests/Expect/throws_A01_t02.dart
@@ -2,14 +2,17 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void throws(void f(), [_CheckExceptionFn check = null, String reason = null])
+/// @assertion static void throws(
+///   void f(), [_CheckExceptionFn check = null, String reason = ''])
 /// typedef bool _CheckExceptionFn(exception)
 /// Calls the function [f] and verifies that it throws an exception.
 /// The optional [check] function can provide additional validation that the
 /// correct exception is being thrown.
+///
 /// @description Checks that if the tested method throws an exception, this
 /// method fails only if the validating function is not null and returns false,
-/// regardless of whether the specified reason is null or not.
+/// regardless of whether the specified reason is empty or not.
+///
 /// @author rodionov
 
 import "../../../Utils/expect.dart";
@@ -34,7 +37,7 @@
   check(goodboy, (e) => false, "not empty");
 }
 
-void check(void f(), [checkFn? ch = null, String? reason = null]) {
+void check(void f(), [checkFn? ch = null, String reason = '']) {
   try {
     Expect.throws(f, ch, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/throws_A01_t03.dart b/Utils/tests/Expect/throws_A01_t03.dart
index 8cfcf84..c3f8ef8 100644
--- a/Utils/tests/Expect/throws_A01_t03.dart
+++ b/Utils/tests/Expect/throws_A01_t03.dart
@@ -2,14 +2,17 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void throws(void f(), [_CheckExceptionFn check = null, String reason = null])
+/// @assertion static void throws(
+///   void f(), [_CheckExceptionFn check = null, String reason = ''])
 /// typedef bool _CheckExceptionFn(exception)
 /// Calls the function [f] and verifies that it throws an exception.
 /// The optional [check] function can provide additional validation that the
 /// correct exception is being thrown.
+///
 /// @description Checks that a function being checked can throw arbitrary value, 
 /// possibly not assignable to Exception. 
 /// Testing with functions that throw null, String and Object.
+///
 /// @author rodionov
 /// @author varlax
 
@@ -45,7 +48,7 @@
   check(badboy3, (e) => false, "not empty");
 }
 
-void check(void f(), [checkFn? ch = null, String? reason = null]) {
+void check(void f(), [checkFn? ch = null, String reason = '']) {
   try {
     Expect.throws(f, ch, reason);
     throw new Exception("ExpectException expected");
diff --git a/Utils/tests/Expect/throws_A01_t04.dart b/Utils/tests/Expect/throws_A01_t04.dart
index 2567397..6137f94 100644
--- a/Utils/tests/Expect/throws_A01_t04.dart
+++ b/Utils/tests/Expect/throws_A01_t04.dart
@@ -2,13 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void throws(void f(), [_CheckExceptionFn check = null, String reason = null])
+/// @assertion static void throws(
+/// void f(), [_CheckExceptionFn check = null, String reason = ''])
 /// typedef bool _CheckExceptionFn(exception)
 /// Calls the function [f] and verifies that it throws an exception.
 /// The optional [check] function can provide additional validation that the
 /// correct exception is being thrown.
+///
 /// @description Checks that the optional check function is called with the
 /// thrown object.
+///
 /// @author varlax
 
 import "../../../Utils/expect.dart";
diff --git a/Utils/tests/Expect/throws_A01_t05.dart b/Utils/tests/Expect/throws_A01_t05.dart
index 675f265..9f99cb9 100644
--- a/Utils/tests/Expect/throws_A01_t05.dart
+++ b/Utils/tests/Expect/throws_A01_t05.dart
@@ -2,13 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void throws(void f(), [_CheckExceptionFn check = null, String reason = null])
+/// @assertion static void throws(
+///   void f(), [_CheckExceptionFn check = null, String reason = ''])
 /// typedef bool _CheckExceptionFn(exception)
 /// Calls the function [f] and verifies that it throws an exception.
 /// The optional [check] function can provide additional validation that the
 /// correct exception is being thrown.
+///
 /// @description Checks that exception thrown by the optional check function is
 /// not caught.
+///
 /// @author varlax
 
 import "../../../Utils/expect.dart";
diff --git a/Utils/tests/Expect/throws_A02_t01.dart b/Utils/tests/Expect/throws_A02_t01.dart
index 383e8dd..e682acd 100644
--- a/Utils/tests/Expect/throws_A02_t01.dart
+++ b/Utils/tests/Expect/throws_A02_t01.dart
@@ -2,11 +2,14 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-/// @assertion static void throws(void f(), [_CheckExceptionFn check = null, String reason = null])
+/// @assertion static void throws(
+/// void f(), [_CheckExceptionFn check = null, String reason = ''])
 /// Descriptive error message is provided in case of failure.
-/// @description Checks that message of thrown ExpectException includes the
+///
+/// @description Checks that message of thrown [ExpectException] includes the
 /// specified reason argument if any, both when the tested method doesn't throw
 /// any exceptions and when the check function returns false.
+///
 /// @author varlax
 
 import "../../../Utils/expect.dart";
@@ -23,12 +26,13 @@
 }
 
 
-void check(test tFun, [checkFn? checkFun = null, String? reason = null]) {
+void check(test tFun, [checkFn? checkFun = null, String reason = '']) {
   try {
     Expect.throws(tFun, checkFun, reason);
     Expect.fail("ExpectException expected");
   } on ExpectException catch(e) {
     if (!(e.message as String).contains(reason as String, 0))
-      throw "reason ($reason) not mentioned in ExpectException message (${e.message})";
+      throw "reason ($reason) not mentioned in ExpectException message "
+          "(${e.message})";
   }
 }