Abort unit tests in the event of async failure while awaiting a future.

pkg/unittest/lib/src/test_case.dart

Index: pkg/unittest/lib/src/test_case.dart
diff --git a/pkg/unittest/lib/src/test_case.dart b/pkg/unittest/lib/src/test_case.dart
index 03eafd290d6211b421dccba4135c292c7e08559f..fe0d12de644455db83b0e0d5803a06f5a50d17b6 100644
--- a/pkg/unittest/lib/src/test_case.dart
+++ b/pkg/unittest/lib/src/test_case.dart
@@ -99,7 +99,14 @@ class TestCase {
       _startTime = new DateTime.now();
       _runningTime = null;
       ++_callbackFunctionsOutstanding;
-      return _testFunction();
+      var testReturn = _testFunction();
+      // If _testFunction() returned a future, we want to wait for it like we
+      // would a callback, so if a failure occurs while waiting, we can abort.
+      if (testReturn is Future) {
+        ++_callbackFunctionsOutstanding;
+        testReturn.catchError(_errorHandler('Test'))
+            .whenComplete(_markCallbackComplete);
+      }
     }).catchError(_errorHandler('Test')).then((_) {
       _markCallbackComplete();
       if (result == null) {