我可以在Angular 6单元测试中使用“ this”吗？

Question

我最近从Angular 5升级到Angular 6，并开始使用cli。在我仅将Webpack与茉莉花和业力一起使用来运行单元测试之前。我通常编写单元测试的方式是这样的：

describe('ComponentToTest', () => {
  beforeEach(() => {
    this.injector = ReflectiveInjector.resolveAndCreate([
      { provide: DALService, useClass: MockDal },
      RealService
    ]);

    this.datePipe = new DatePipe('en-US');
    this.component2 = this.injector.get(Component2);
    this.dal = this.injector.get(DALService);
    this.realService = this.injector.get(RealService);

    this.componentToTest = new ComponentToTest(
      this.datePipe,
      this.component2,
      this.dal,
      this.realService);

    // Test Data
    this.testData = [1, 2, 3];
  });

  describe('testFunctionOne', () => {
    it('should return true', () => {
      expect(this.componentToTest.testFunctionOne()).toEqual(true);
    });
  });
});

但是对于cli项目，当我运行“ ng test”时，所有测试都失败，并说“ this”未定义。例如。实际错误之一是：

TypeError: Cannot set property 'injector' of undefined

我可以在测试中不再使用'this'吗？一切都必须是在main describe内部声明的变量吗？