如何使用 Jasmine 在 Angular 單元測試中模擬 window.screen.width

Question

我有一個 BreakpointService，它告訴我 - 取決於屏幕寬度 - 我應該在哪個 SidebarMode（關閉 - 縮小 - 打開）中顯示我的側邊欄。

這是服務的主要部分：

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$);
  }

通過這一行，我可以訂閱事件：

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

現在，我想在單元測試中測試不同的模式，但我不知道

如何在測試中模擬 window.screen.width 屬性

我嘗試了幾件事，但對我來說沒有任何效果。

到目前為止，這是我的測試設置：

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 會監聽 resize 事件，所以也許您可以嘗試使用 jasmine 模擬 window.innerWidth / window.outerWidth 之類的東西？

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

然后您手動觸發調整大小事件：

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

它看起來像這樣：

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

Answer 2

Mocking Angular Material BreakpointObserver

我猜你不是真的想模擬 window.screen，你實際上想模擬BreakpointObserver 。 畢竟，不需要測試他們的代碼，您只想測試您的代碼是否正確響應BreakpointObserver.observe()返回的具有不同屏幕尺寸的 observable。

有很多不同的方法可以做到這一點。 為了說明一種方法，我將STACKBLITZ與您的代碼放在一起，展示了我將如何處理此問題。 與上面的代碼不同的注意事項：

• 您的代碼在構造函數中設置了 observable。 因此，必須在實例化服務之前更改模擬，因此您將看到對resize()的調用發生在service = TestBed.get(MyService);之前service = TestBed.get(MyService); 稱呼。
• 我嘲笑BreakpointObserver與spyObj，並呼吁在地方的假冒功能BreakpointObserver.observe()方法。 這個假函數使用了我設置的過濾器，其中包含我想要的各種匹配結果。 它們都以 false 開始，因為這些值會根據需要模擬的屏幕尺寸而改變，而這是由您在上面的代碼中使用的resize()函數設置的。

注意：當然還有其他方法可以解決這個問題。 在 github 上查看 angular 材料自己的breakpoints-observer.spec.ts 。 這是一種比我在這里概述的更好的通用方法，它只是為了測試您提供的功能。

這是來自 StackBlitz 的新建議describe函數的片段：

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 的測試，您會得到答案。 您不需要模擬 BreakpointObserver，您需要模擬注入其中的 MediaMatcher。 這是我的一項測試。

        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();
                });
            });
        });