anchor.diff:    /// Returns a new instance of [NgTestBed] with [stabilizers] added.
     NgTestBed<T> addStabilizers(Iterable<NgTestStabilizerFactory> stabilizers) {
       return fork(
  -      stabilizer: composeStabilizers([_createStabilizer]..addAll(stabilizers)),
  +      stabilizer: composeStabilizers([_createStabilizer, ...stabilizers]),
       );
     }
   
  
positive.code: 
  /// Used to determine if there is an actively executing test.
  NgTestFixture<Object> activeTest;
  
  /// Returns a new [List] merging iterables [a] and [b].
  List<E> _concat<E>(Iterable<E> a, Iterable<E> b) {
    return a.toList()..addAll(b);
  }
  
  /// If any [NgTestFixture] is currently executing, calls `dispose` on it.
  ///
  
negative.code:     if (_usesComponentFactory) {
        throw UnsupportedError('Use "addInjector" instead');
      }
      return fork(providers: [..._providers, ...providers]);
    }
  
    /// Returns a new instance of [NgTestBed] with the root injector wrapped.
  