anchor.diff:      testCase.error(
           'Async tests must wait for at least one callback ', '');
     }
  +}
  +
  +/**
  + * Creates a new test case with the given description and body. The
  + * description will include the descriptions of any surrounding group()
  + * calls.
  + *
  + * "solo_" means that this will be the only test that is run. All other tests
  + * will be skipped. This is a convenience function to let you quickly isolate
  + * a single test by adding "solo_" before it to temporarily disable all other
  + * tests.
  + */
  +void solo_test(String spec, TestFunction body) {
  +  // TODO(rnystrom): Support multiple solos. If more than one test is solo-ed,
  +  // all of the solo-ed tests and none of the non-solo-ed ones should run.
  +  if (_soloTest != null) {
  +    throw new Exception('Only one test can be soloed right now.');
  +  }
  +
  +  ensureInitialized();
  +
  +  _soloTest = new TestCase(_tests.length + 1, _fullSpec(spec), body, 0);
  +  _tests.add(_soloTest);
   }
   
   /** Sentinel value for [_SpreadArgsHelper]. */
  
positive.code: 
  /** Runs all queued tests, one at a time. */
  _runTests() {
    _config.onStart();
  
    _defer(() {
  
negative.code:   return _currentGroup != '' ? '$_currentGroup $spec' : spec;
  }
  
  void _fail(String message) {
    throw new ExpectException(message);
  }
  
  /**
   * Lazily initializes the test library if not already initialized.
   */
  