anchor.diff:    /// by setting [watchAngularLifecycle] to `false`.
     factory NgTestBed({
       Element host,
  +    InjectorFactory rootInjector,
       bool watchAngularLifecycle: true,
     }) {
       if (T == dynamic) {
  
positive.code:     }
      return new NgTestBed<T>._allowDynamicType(
        host: host,
        watchAngularLifecycle: watchAngularLifecycle,
      );
    }
  
negative.code:   // Used for compatibility only.
    factory NgTestBed._allowDynamicType({
      Element host,
      InjectorFactory rootInjector,
      bool watchAngularLifecycle: true,
    }) {
      return new NgTestBed<T>._(
        host: host,
        providers: const [],
        stabilizers: watchAngularLifecycle ? _lifecycleStabilizers : const [],
        rootInjector: rootInjector,
      );
    }
  
  