unit-testing - Angular2/Jasmine 期望为 null 使浏览器崩溃

我在测试我的一个组件时遇到了一些麻烦。测试如下:

describe('SmpEventsNewCompactEventComponent', () => {

  const specService: SmpSpecService = new SmpSpecService();

  describe('Component rendering', () => {
    let componentInstance: any;
    let componentFixture: ComponentFixture<any>;
    let cssSelector: string;

    beforeEach(() => {
      TestBed.configureTestingModule({
        imports: [
          MaterialModule.forRoot()
        ],
        declarations: [
          SmpEventsCompactEventComponent,
          SmpEventsAddressComponent
        ],
        providers: [
          { provide: SMP_OT_HELPER, useValue: newOtHelperInstance() },
          DatePipe,
          SmpEventTypeCheckerService,
          SmpLangService
        ]
      });

      componentFixture = TestBed.createComponent(SmpEventsCompactEventComponent);
      componentInstance = componentFixture.componentInstance;
    });

    describe('Global', () => {
      it('GIVEN there are date/time AND address ' +
        'WHEN component loads THEN display event', () => {
          //// TEST ONE
          componentInstance.isEventEnabled = true;
          cssSelector = '.events-compact-event';

          let debugElement = specService.queryDebugElement(
            componentFixture, cssSelector);

          expect(debugElement).not.toBeNull();
        });

      it('GIVEN there are no date/time AND no address ' +
        'WHEN component loads THEN do not display event', () => {
          //// TEST TWO
          componentInstance.isEventEnabled = true;
          //componentInstance.isAddressEnabled = false;
          // componentInstance.isDateEnabled = false;
          cssSelector = '.events-compact-event';

          let debugElement = specService.queryDebugElement(
            componentFixture, cssSelector);

            console.log('--------------', debugElement.nativeElement);
          // expect(debugElement.nativeElement).toBe(null);
          // expect(true).toBe(true);
          expect(debugElement).not.toBeNull();
        });
    });
});

specService.queryDebugElement 如下:

  queryDebugElement(fixture: ComponentFixture<any>, cssSelector: string): DebugElement {
    fixture.detectChanges();

    return fixture.debugElement.query(By.css(cssSelector));
  }

每当我使用

expect(true).toBe(true);

或者

expect(debugElement.nativeElement).toBe(null);

或者

expect(debugElement).not.toBeNull();

在测试二中，测试正常工作或失败，但每当我使用

expect(debugElement).toBeNull();

karma crash 使用的浏览器(使用 chrome/chromium/PhantomJs 测试)并且没有给出任何关于发生了什么的线索。这不是一个简单的“期望假为真”失败，测试上下文完全崩溃。

你看到什么可以解释这种行为了吗？

最佳答案

使用 expect(debugElement).toBeTruthy(); 而不是 expect(debugElement).not.toBeNull() 因为当某些事情未定义时 not.tobeNull() 可能不会按预期运行。如果您的 debugElement 未定义，则可能会产生问题。