如何测试使用商店选择器的 NGRX 效果？

Question

我有一个@Effect，它使用MemoizedSelector 从redux 存储中获取一个项目，并使用mergeMap 它和一个Action 的有效负载。效果很好，但是为此设置 Jest 测试证明很困难，因为我似乎无法模拟选择器的返回值，因为 select 是一个已声明的导入函数（来自 '@ngrx/store ') 并在效果中使用，并且选择器本身也是一个导入函数。我现在正抓着稻草。

如何编写单元测试来测试使用商店选择器的 NGRX 效果？
"@ngrx/store": "^7.4.0",
"rxjs": "^6.2.2"

我尝试了以下几种解决方案：

1. 使用

provideMockStore({
  initialState
})

provideMockStore 来自'@ngrx/store/testing';，其中初始状态既是我的实际 initialState，也是包含我要选择的确切结构/项目的状态

1. 使用来自各种 SO 问题/答案的不同类型的 MockStore 以及不同的博客文章方法

   • Mock ngrx store selectors in unit tests (Angular)
   • https://blog.angularindepth.com/how-i-test-my-ngrx-selectors-c50b1dc556bc
   • https://christianlydemann.com/the-complete-guide-to-ngrx-testing/
   • https://medium.com/@adrianfaciu/testing-ngrx-effects-3682cb5d760e

2. 尝试使用<selector>.projector(<my-mock-object>) 模拟选择器（这里是草根，我很确定这将用于选择器而不是效果的隔离测试）

效果本身：

@Effect()
  getReviewsSuccess$ = this.actions$.pipe(
    ofType<ProductActions.GetReviewsSuccess>(
      ProductActions.ProductActionTypes.GET_REVIEWS_SUCCESS
    ),
    mergeMap(() => this.reduxStore.pipe(select(selectProduct))),
    map(({ product_id }) => product_id),
    map(product_id => new ProductActions.GetReviewsMeta({
      product_id,
    }))
  );

规格：

......
  let effects: ProductEffects;
  let facade: Facade;
  let actions$: Observable<any>;
  let store$: Observable<State>;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [
        RouterTestingModule,
        // ^ I've also tried using StoreModule.forRoot(...) here to configure 
        // it in similar fashion to the module where this effect lives
      ],
      providers: [
        ProductEffects,
        provideMockActions(() => actions$),
        {
          provide: Facade,
          useValue: facadeServiceMock,
        },
        ResponseService,
        provideMockStore({
          initialState
        })
        // ^ also tried setting up the test with different variations of initialState
      ],
    });
......

it('should return a GetReviewsMeta on successful GetReviewsSuccess', () => {
    const reviews = {...reviewListMock};
    const { product_id } = {...productMockFull};

    const action = new ProductActions.GetReviewsSuccess({
      reviews
    });

    const outcome = new ProductActions.GetReviewsMeta({
      product_id
    });

    actions$ = hot('-a', { a: action }); 

    // store$ = cold('-c', { c: product_id });  
    // not sure what, if anything I need to do here to mock select(selectProduct)  

    const expected = cold('-b', { b: outcome });  
    expect(effects.getReviewsSuccess$).toBeObservable(expected);
  });

选择器selectProduct：

export const getProduct = ({product}: fromProducts.State) => product;

export const getProductState = createFeatureSelector<
    fromProducts.State
>('product');

export const selectProduct = createSelector(
  getProductState,
  getProduct,
);

我希望测试通过，但我不断收到以下错误

● Product Effects › should return a GetReviewsMeta on successful GetReviewsSuccess

    expect(received).toBeNotifications(expected)

    Expected notifications to be:
      [{"frame": 10, "notification": {"error": undefined, "hasValue": true, "kind": "N", "value": {"payload": {"product_id": 2521}, "type": "[Reviews] Get Reviews Meta"}}}]
    But got:
      [{"frame": 10, "notification": {"error": [TypeError: Cannot read property 'product_id' of undefined], "hasValue": false, "kind": "E", "value": undefined}}]

显然MemoizedSelector (selectProduct) 不知道应该在商店中的产品对象是什么（但似乎不知道我是否注入了具有它的initialState）并且可以'无法获得产品的product_id，因为我没有在beforeEach 或规范本身中正确设置它...

Answer 1

我们在ngrx.io 文档中对此进行了介绍。请注意，语法适用于 NgRx 8，但相同的想法适用于 NgRx 7。

addBookToCollectionSuccess$ = createEffect(
    () =>
      this.actions$.pipe(
        ofType(CollectionApiActions.addBookSuccess),
        withLatestFrom(this.store.pipe(select(fromBooks.getCollectionBookIds))),
        tap(([, bookCollection]) => {
          if (bookCollection.length === 1) {
            window.alert('Congrats on adding your first book!');
          } else {
            window.alert('You have added book number ' + bookCollection.length);
          }
        })
      ),
    { dispatch: false }
  );

it('should alert number of books after adding the second book', () => {
      store.setState({
        books: {
          collection: {
            loaded: true,
            loading: false,
            ids: ['1', '2'],
          },
        },
      } as fromBooks.State);

      const action = CollectionApiActions.addBookSuccess({ book: book1 });
      const expected = cold('-c', { c: action });
      actions$ = hot('-a', { a: action });
      expect(effects.addBookToCollectionSuccess$).toBeObservable(expected);
      expect(window.alert).toHaveBeenCalledWith('You have added book number 2');
    });
  });

确保您的 state 与 redux devtools 中的结构相同。

NgRx 8 还提供了一种模拟选择器的方法，因此不需要为单个测试设置整个状态树 - https://next.ngrx.io/guide/store/testing#using-mock-selectors。

describe('Auth Guard', () => {
  let guard: AuthGuard;
  let store: MockStore<fromAuth.State>;
  let loggedIn: MemoizedSelector<fromAuth.State, boolean>;

  beforeEach(() => {
    TestBed.configureTestingModule({
      providers: [AuthGuard, provideMockStore()],
    });

    store = TestBed.get(Store);
    guard = TestBed.get(AuthGuard);

    loggedIn = store.overrideSelector(fromAuth.getLoggedIn, false);
  });

  it('should return false if the user state is not logged in', () => {
    const expected = cold('(a|)', { a: false });

    expect(guard.canActivate()).toBeObservable(expected);
  });

  it('should return true if the user state is logged in', () => {
    const expected = cold('(a|)', { a: true });

    loggedIn.setResult(true);

    expect(guard.canActivate()).toBeObservable(expected);
  });
});