Angular2/Jasmine期望为null使浏览器崩溃

Question

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);

要么

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

要么

expect(debugElement).not.toBeNull();

在TEST TWO中,无论何时使用,测试都会正常工作或失败

expect(debugElement).toBeNull();

因业力崩溃使用的浏览器(使用chrome/chromium/PhantomJs测试)并没有提供任何发生的线索.这不是一个简单的"期望错误是真的"失败,测试上下文完全崩溃.

你看到任何可以解释这种行为的东西吗？

Answer 1

Angular DebugElement是一个相当复杂的对象,Jasmine expect似乎包含递归部分(或者至少是复杂到足以需要许多不同函数调用的算法)......因此DebugElement不建议直接在单元测试中使用.它通常以深度递归和浏览器内存泄漏结束.

在你的情况下,我会尝试:

let nl: NodeList = componentFixture.nativeElement.querySelectorAll('.events-compact-event');

expect(nl.length).toBeFalsy;

这样,您就不会使用DebugElement,并且您不会在测试中有未定义值的风险(除了您需要未定义的值).代码覆盖率和结果应该是等效的.

看看这篇文章:https://medium.com/@martatatiana/poor-detective-angular2-browser-crash-and-debugelement-f0a651dbf33