anchor.diff:  /**
    * Registers that an exception was caught for the current test.
    */
  -_registerException(testNum, e, [trace]) {
  +void _registerException(testNum, e, [trace]) {
     trace = trace == null ? '' : trace.toString();
     String message = (e is TestFailure) ? e.message : 'Caught $e';
     if (_tests[testNum].result == null) {
  
positive.code:  * running. Tests will resume executing when such asynchronous test calls
   * [done] or if it fails with an exception.
   */
  _nextBatch() {
    while (true) {
      if (_currentTest >= _tests.length) {
        _completeTests();
  
negative.code:   wrapAsync = (f, [id]) => expectAsync1(f, id: id);
  
    _tests = <TestCase>[];
    _uncaughtErrorMessage = null;
  
    if (_config == null) {
  