如何使用 Jasmine 在 Angular 单元测试中模拟 window.screen.width

Question

我有一个 BreakpointService，它告诉我 - 根据屏幕宽度 - 我应该在哪个 SidebarMode（关闭 - 缩小 - 打开）中显示我的边栏。

这是服务的主要部分：

constructor(private breakpointObserver: BreakpointObserver) {
    this.closed$ = this.breakpointObserver.observe(['(min-width: 1024px)']).pipe(
      filter((state: BreakpointState) => !state.matches),
      mapTo(SidebarMode.Closed)
    );

    this.opened$ = this.breakpointObserver.observe(['(min-width: 1366px)']).pipe(
      filter((state: BreakpointState) => state.matches),
      mapTo(SidebarMode.Open)
    );

    const minifiedStart$: Observable<boolean> = this.breakpointObserver.observe(['(min-width: 1024px)']).pipe(map(state => state.matches));

    const minifiedEnd$: Observable<boolean> = this.breakpointObserver.observe(['(max-width: 1366px)']).pipe(map(state => state.matches));

    this.minified$ = minifiedStart$.pipe(
      flatMap(start => minifiedEnd$.pipe(map(end => start && end))),
      distinctUntilChanged(),
      filter(val => val === true),
      mapTo(SidebarMode.Minified)
    );

    this.observer$ = merge(this.closed$, this.minified$, this.opened$);
  }

通过这一行，我可以订阅事件：

this.breakpointService.observe().subscribe();

现在，我想在单元测试中测试不同的模式，但我不知道

如何在测试中模拟 window.screen.width 属性

我尝试了几件事，但没有任何结果。

这是我目前的测试设置：

describe('observe()', () => {
    function resize(width: number): void {
      // did not work
      // window.resizeTo(width, window.innerHeight);
      // (<any>window).screen = { width: 700 };
      // spyOn(window, 'screen').and.returnValue(...)
    }

    let currentMode;
    beforeAll(() => {
      service.observe().subscribe(mode => (currentMode = mode));
    });

    it('should return Observable<SidebarMode>', async () => {
      resize(1000);

      expect(Object.values(SidebarMode).includes(SidebarMode[currentMode])).toBeTruthy();
    });

    xit('should return SidebarMode.Closed', async () => {
      resize(600);

      expect(currentMode).toBe(SidebarMode.Closed);
    });

    xit('should return SidebarMode.Minified', async () => {
      resize(1200);

      expect(currentMode).toBe(SidebarMode.Minified);
    });

    xit('should return SidebarMode.Open', async () => {
      resize(2000);

      expect(currentMode).toBe(SidebarMode.Open);
    });
  });

Answer 1

我猜 BreakPointObserver 会监听 resize 事件，所以也许您可以尝试使用 jasmine 模拟 window.innerWidth / window.outerWidth 之类的东西？

spyOnProperty(window, 'innerWidth').and.returnValue(760);

然后你手动触发一个resize事件：

window.dispatchEvent(new Event('resize'));

看起来是这样的：

    it('should mock window inner width', () => {
        spyOnProperty(window, 'innerWidth').and.returnValue(760);
        window.dispatchEvent(new Event('resize'));
    });

Answer 2

模拟 Angular 材质 BreakpointObserver

我猜你并不是真的想模拟 window.screen，你实际上是想模拟 BreakpointObserver。毕竟，无需测试他们的代码，您只需测试您的代码是否正确响应 BreakpointObserver.observe() 返回的不同屏幕尺寸的 observable。

有很多不同的方法可以做到这一点。为了说明一种方法，我将STACKBLITZ 与您的代码放在一起，展示了我将如何处理这个问题。与您上面的代码不同的注意事项：

• 您的代码在构造函数中设置了可观察对象。因此，必须在实例化服务之前更改模拟，因此您会看到对 resize() 的调用发生在 service = TestBed.get(MyService); 调用之前。
• 我用 spyObj 嘲笑了BreakpointObserver，并称其为假 代替BreakpointObserver.observe() 方法的函数。这 假函数使用我设置的过滤器，得到我想要的结果 从各种比赛中。他们一开始都是假的，因为 值会根据所需的屏幕尺寸而改变 模拟，这是由您使用的 resize() 函数设置的 在上面的代码中。

注意：当然还有其他方法可以解决这个问题。查看角材料自己的breakpoints-observer.spec.tson github。这是一种比我在这里概述的更好的通用方法，它只是为了测试您提供的功能。

这是 StackBlitz 中新建议的 describe 函数的片段：

describe(MyService.name, () => {
  let service: MyService;
  const matchObj = [
    // initially all are false
    { matchStr: '(min-width: 1024px)', result: false },
    { matchStr: '(min-width: 1366px)', result: false },
    { matchStr: '(max-width: 1366px)', result: false },
  ];
  const fakeObserve = (s: string[]): Observable<BreakpointState> =>
    from(matchObj).pipe(
      filter(match => match.matchStr === s[0]),
      map(match => ({ matches: match.result, breakpoints: {} })),
    );
  const bpSpy = jasmine.createSpyObj('BreakpointObserver', ['observe']);
  bpSpy.observe.and.callFake(fakeObserve);
  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [],
      providers: [MyService, { provide: BreakpointObserver, useValue: bpSpy }],
    });
  });

  it('should be createable', () => {
    service = TestBed.inject(MyService);
    expect(service).toBeTruthy();
  });

  describe('observe()', () => {
    function resize(width: number): void {
      matchObj[0].result = width >= 1024;
      matchObj[1].result = width >= 1366;
      matchObj[2].result = width <= 1366;
    }

    it('should return Observable<SidebarMode>', () => {
      resize(1000);
      service = TestBed.inject(MyService);
      service.observe().subscribe(mode => {
        expect(
          Object.values(SidebarMode).includes(SidebarMode[mode]),
        ).toBeTruthy();
      });
    });

    it('should return SidebarMode.Closed', () => {
      resize(600);
      service = TestBed.inject(MyService);
      service
        .observe()
        .subscribe(mode => expect(mode).toBe(SidebarMode.Closed));
    });

    it('should return SidebarMode.Minified', () => {
      resize(1200);
      service = TestBed.inject(MyService);
      service
        .observe()
        .subscribe(mode => expect(mode).toBe(SidebarMode.Minified));
    });

    it('should return SidebarMode.Open', () => {
      resize(2000);
      service = TestBed.inject(MyService);
      service.observe().subscribe(mode => expect(mode).toBe(SidebarMode.Open));
    });
  });
});

Answer 3

如果您查看 BreakpointObserver 的测试，您会得到答案。您不需要模拟 BreakpointObserver，您需要模拟注入其中的 MediaMatcher。这是我的一项测试。

        let mediaMatcher: FakeMediaMatcher;

        class FakeMediaQueryList {
            /** The callback for change events. */
            private listeners: ((mql: MediaQueryListEvent) => void)[] = [];

            constructor(public matches: boolean, public media: string) {}

            /** Toggles the matches state and "emits" a change event. */
            setMatches(matches: boolean): void {
                this.matches = matches;

                /** Simulate an asynchronous task. */
                setTimeout(() => {
                    // tslint:disable-next-line: no-any
                    this.listeners.forEach((listener) => listener(this as any));
                });
            }

            /** Registers a callback method for change events. */
            addListener(callback: (mql: MediaQueryListEvent) => void): void {
                this.listeners.push(callback);
            }

            /** Removes a callback method from the change events. */
            removeListener(callback: (mql: MediaQueryListEvent) => void): void {
                const index = this.listeners.indexOf(callback);

                if (index > -1) {
                    this.listeners.splice(index, 1);
                }
            }
        }

        @Injectable()
        class FakeMediaMatcher {
            /** A map of match media queries. */
            private queries = new Map<string, FakeMediaQueryList>();

            /** The number of distinct queries created in the media matcher during a test. */
            get queryCount(): number {
                return this.queries.size;
            }

            /** Fakes the match media response to be controlled in tests. */
            matchMedia(query: string): FakeMediaQueryList {
                const mql = new FakeMediaQueryList(true, query);
                this.queries.set(query, mql);
                return mql;
            }

            /** Clears all queries from the map of queries. */
            clear(): void {
                this.queries.clear();
            }

            /** Toggles the matching state of the provided query. */
            setMatchesQuery(query: string, matches: boolean): void {
                const mediaListQuery = this.queries.get(query);
                if (mediaListQuery) {
                    mediaListQuery.setMatches(matches);
                } else {
                    throw Error('This query is not being observed.');
                }
            }
        }

        beforeEach(async () => {
            await TestBed.configureTestingModule({
                providers: [
                    { provide: MediaMatcher, useClass: FakeMediaMatcher },
                ],
            });
        });

        beforeEach(inject([MediaMatcher], (mm: FakeMediaMatcher) => {
            mediaMatcher = mm;
        }));

        afterEach(() => {
            mediaMatcher.clear();
        });

        describe('get isSideNavClosable$', () => {
            beforeEach(() => {
                // (Andrew Alderson Jan 1, 2020) need to do this to register the query
                component.isSideNavClosable$.subscribe();
            });
            it('should emit false when the media query does not match', (done) => {
                mediaMatcher.setMatchesQuery('(max-width: 1280px)', false);

                component.isSideNavClosable$.subscribe((closeable) => {
                    expect(closeable).toBeFalsy();
                    done();
                });
            });
            it('should emit true when the media query does match', (done) => {
                mediaMatcher.setMatchesQuery('(max-width: 1280px)', true);

                component.isSideNavClosable$.subscribe((closeable) => {
                    expect(closeable).toBeTruthy();
                    done();
                });
            });
        });