Fix issue 4227 - unittest.dart silently consumes exceptions when expectAsync is active.

tests/lib/unittest/unittest_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 // TODO(gram):
 // Unfortunately I can't seem to test anything that involves timeouts, e.g.
 // insufficient callbacks, because the timeout is controlled externally
 // (test.dart?), and we would need to use a shorter timeout for the inner tests
 // so the outer timeout doesn't fire. So I removed all such tests.
 // I'd like to revisit this at some point.
@@ skipping 105 matching lines @@
       test(testName, () {
              var _callback;
              _callback = expectAsyncUntil0(() {
                if (++_testconfig.count < 10) {
                  _defer(_callback);
                }
              },
              () => (_testconfig.count == 10));
              _defer(_callback);
       });
+    } else if (testName == 'async exception test') {
+      test(testName, () {
+        expectAsync0(() {});
+        _defer(() => guardAsync(() { throw "error!"; }));
+      });
     }
   });
 }
 
 void nextTest(int testNum) {
   SendPort sport = spawnFunction(runTest);
   sport.call(tests[testNum]).then((msg) {
     actual.add(msg);
     if (actual.length == expected.length) {
       for (var i = 0; i < tests.length; i++) {
         test(tests[i], () => expect(actual[i].trim(), equals(expected[i])));
       }
     } else {
       nextTest(testNum+1);
     }
   });
 }
 
 main() {
   tests = [
     'single correct test',
     'single failing test',
     'exception test',
     'group name test',
     'setup test',
     'teardown test',
     'setup and teardown test',
     'correct callback test',
     'excess callback test',
-    'completion test'
+    'completion test',
+    'async exception test'
   ];
 
   expected = [
     buildStatusString(1, 0, 0, tests[0]),
     buildStatusString(0, 1, 0, tests[1],
         message: 'Expected: <5> but: was <4>.'),
     buildStatusString(0, 1, 0, tests[2], message: 'Caught Exception: Fail.'),
     buildStatusString(2, 0, 0, 'a a::a b b'),
     buildStatusString(1, 0, 0, 'a ${tests[4]}', 0, 'setup'),
     buildStatusString(1, 0, 0, 'a ${tests[5]}', 0, '', 'teardown'),
     buildStatusString(1, 0, 0, 'a ${tests[6]}', 0,
         'setup', 'teardown'),
     buildStatusString(1, 0, 0, tests[7], 1),
     buildStatusString(0, 0, 1, tests[8], 1,
         message: 'Callback called more times than expected (2 > 1).'),
-    buildStatusString(1, 0, 0, tests[9], 10)
+    buildStatusString(1, 0, 0, tests[9], 10),
+    buildStatusString(0, 0, 1, tests[10], message: 'Caught error!'),
   ];
 
   actual = [];
 
   nextTest(0);
 }