anchor.diff:    };
   }
   
  -void _throwMockArgumentError(method) =>
  -    throw new ArgumentError('$method must only be given a Mock object');
  +void _throwMockArgumentError(String method, var nonMockInstance) {
  +  if (nonMockInstance == null) {
  +    throw ArgumentError('$method was called with a null argument');
  +  }
  +  throw ArgumentError('$method must only be given a Mock object');
  +}
   
   void verifyNoMoreInteractions(var mock) {
     if (mock is Mock) {
  
positive.code:           mock._realCalls.join());
      }
    } else {
      _throwMockArgumentError('verifyZeroInteractions');
    }
  }
  
  
negative.code:       fail("No more calls expected, but following found: " + unverified.join());
      }
    } else {
      _throwMockArgumentError('verifyNoMoreInteractions', mock);
    }
  }
  
  