Upgrade to test 0.12.0.

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1145403002
diff --git a/pubspec.yaml b/pubspec.yaml
index 4a3b1f6..cb373be 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: args
-version: 0.13.0
+version: 0.13.1-dev
 author: "Dart Team <misc@dartlang.org>"
 homepage: https://github.com/dart-lang/args
 description: >
@@ -7,6 +7,6 @@
  a set of options and values using GNU and POSIX style options.
 
 dev_dependencies:
-  unittest: ">=0.11.5 <0.12.0"
+  test: ">=0.12.0 <0.13.0"
 environment:
   sdk: ">=1.4.0 <2.0.0"
diff --git a/test/args_test.dart b/test/args_test.dart
index b22d0c9..ee37b45 100644
--- a/test/args_test.dart
+++ b/test/args_test.dart
@@ -4,7 +4,7 @@
 
 library args_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:args/args.dart';
 import 'utils.dart';
 
diff --git a/test/command_parse_test.dart b/test/command_parse_test.dart
index e336e71..54b3032 100644
--- a/test/command_parse_test.dart
+++ b/test/command_parse_test.dart
@@ -4,7 +4,7 @@
 
 library command_parse_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:args/args.dart';
 import 'utils.dart';
 
diff --git a/test/command_runner_test.dart b/test/command_runner_test.dart
index 904a038..3a796f1 100644
--- a/test/command_runner_test.dart
+++ b/test/command_runner_test.dart
@@ -5,7 +5,7 @@
 library command_runner_test;
 
 import 'package:args/command_runner.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 import 'utils.dart';
 
diff --git a/test/command_test.dart b/test/command_test.dart
index fe3446c..888016a 100644
--- a/test/command_test.dart
+++ b/test/command_test.dart
@@ -5,7 +5,7 @@
 library command_test;
 
 import 'package:args/command_runner.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'utils.dart';
 
 void main() {
diff --git a/test/parse_test.dart b/test/parse_test.dart
index 502210a..ba7453c 100644
--- a/test/parse_test.dart
+++ b/test/parse_test.dart
@@ -4,7 +4,7 @@
 
 library parse_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:args/args.dart';
 import 'utils.dart';
 
diff --git a/test/trailing_options_test.dart b/test/trailing_options_test.dart
index 24f6ce7..efc53b2 100644
--- a/test/trailing_options_test.dart
+++ b/test/trailing_options_test.dart
@@ -4,7 +4,7 @@
 
 library trailing_options_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:args/args.dart';
 
 void main() {
diff --git a/test/usage_test.dart b/test/usage_test.dart
index e7f3e47..51efc05 100644
--- a/test/usage_test.dart
+++ b/test/usage_test.dart
@@ -4,7 +4,7 @@
 
 library usage_test;
 
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 import 'package:args/args.dart';
 
 void main() {
diff --git a/test/utils.dart b/test/utils.dart
index 9d85fb0..1cdd803 100644
--- a/test/utils.dart
+++ b/test/utils.dart
@@ -8,7 +8,7 @@
 
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
-import 'package:unittest/unittest.dart';
+import 'package:test/test.dart';
 
 class CommandRunnerWithFooter extends CommandRunner {
   final usageFooter = "Also, footer!";