Add matchers for unit testing futures:

tests/utils/unittest_test.dart

Index: tests/utils/unittest_test.dart
diff --git a/tests/utils/unittest_test.dart b/tests/utils/unittest_test.dart
index 74d8b2d455675899e87bc230774c743261dfb0ab..cb8b70d31d87439f561bef2ffbfe53ca31d27eff 100644
--- a/tests/utils/unittest_test.dart
+++ b/tests/utils/unittest_test.dart
@@ -28,10 +28,11 @@ void shouldFail(var value, Matcher matcher, expected) {
   expect(value, matcher);
   configureExpectHandler(null);
   expect(errorCount, equals(1));
-  if (expected is String)
+  if (expected is String) {
     expect(errorString, equalsIgnoringWhitespace(expected));
-  else
-   expect(errorString, expected);
+  } else {
+    expect(errorString, expected);
+  }
 }
 
 void shouldPass(var value, Matcher matcher) {