Merge pull request #118 from MichaelRFairhurst/void-fixes

Changes for landing https://github.com/dart-lang/sdk/issues/32161
diff --git a/test/hit_types_test.dart b/test/hit_types_test.dart
index e8bf241..a7ee490 100644
--- a/test/hit_types_test.dart
+++ b/test/hit_types_test.dart
@@ -11,7 +11,7 @@
 
 import 'src/common.dart';
 
-main() => defineTests();
+void main() => defineTests();
 
 void defineTests() {
   group('screenView', () {
diff --git a/test/src/common.dart b/test/src/common.dart
index 7799394..c2f1a5e 100644
--- a/test/src/common.dart
+++ b/test/src/common.dart
@@ -12,9 +12,9 @@
 AnalyticsImplMock createMock({Map<String, dynamic> props}) =>
     new AnalyticsImplMock('UA-0', props: props);
 
-was(Map m, String type) => expect(m['t'], type);
-has(Map m, String key) => expect(m[key], isNotNull);
-hasnt(Map m, String key) => expect(m[key], isNull);
+void was(Map m, String type) => expect(m['t'], type);
+void has(Map m, String key) => expect(m[key], isNotNull);
+void hasnt(Map m, String key) => expect(m[key], isNull);
 
 class AnalyticsImplMock extends AnalyticsImpl {
   MockProperties get mockProperties => properties;
diff --git a/test/usage_impl_io_test.dart b/test/usage_impl_io_test.dart
index 7f1719c..a9c30d4 100644
--- a/test/usage_impl_io_test.dart
+++ b/test/usage_impl_io_test.dart
@@ -11,7 +11,7 @@
 import 'package:test/test.dart';
 import 'package:usage/src/usage_impl_io.dart';
 
-main() => defineTests();
+void main() => defineTests();
 
 void defineTests() {
   group('IOPostHandler', () {
diff --git a/test/usage_impl_test.dart b/test/usage_impl_test.dart
index a4ca3ac..2a3ea35 100644
--- a/test/usage_impl_test.dart
+++ b/test/usage_impl_test.dart
@@ -9,7 +9,7 @@
 
 import 'src/common.dart';
 
-main() => defineTests();
+void main() => defineTests();
 
 void defineTests() {
   group('ThrottlingBucket', () {
diff --git a/test/usage_test.dart b/test/usage_test.dart
index 37500a9..d97d7b4 100644
--- a/test/usage_test.dart
+++ b/test/usage_test.dart
@@ -7,7 +7,7 @@
 import 'package:test/test.dart';
 import 'package:usage/usage.dart';
 
-main() => defineTests();
+void main() => defineTests();
 
 void defineTests() {
   group('AnalyticsMock', () {
diff --git a/test/uuid_test.dart b/test/uuid_test.dart
index 98dbab8..81762e7 100644
--- a/test/uuid_test.dart
+++ b/test/uuid_test.dart
@@ -7,7 +7,7 @@
 import 'package:test/test.dart';
 import 'package:usage/uuid/uuid.dart';
 
-main() => defineTests();
+void main() => defineTests();
 
 void defineTests() {
   group('uuid', () {