Ability to guard callbacks that may never get called.

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 157 matching lines @@
     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(0, 0, 1, tests[10], message: 'Caught error!'),
+    buildStatusString(0, 1, 0, tests[10], message: 'Caught error!'),
   ];
 
   actual = [];
 
   nextTest(0);
 }