feat(store): add API to mock selector return value

Closes #1504

modules/store/spec/selector.spec.ts

@@ -47,6 +47,20 @@ describe('Selectors', () => {
       expect(projectFn).toHaveBeenCalledWith(countOne, countTwo);
     });
 
+    it('should allow an override of the selector return', () => {
+      const projectFn = jasmine.createSpy('projectionFn').and.returnValue(2);
+
+      const selector = createSelector(incrementOne, incrementTwo, projectFn);
+
+      expect(selector.projector()).toBe(2);
+
+      selector.setResult(5);
+
+      const result2 = selector({});
+
+      expect(result2).toBe(5);
+    });
+
     it('should be possible to test a projector fn independent from the selectors it is composed of', () => {
       const projectFn = jasmine.createSpy('projectionFn');
       const selector = createSelector(incrementOne, incrementTwo, projectFn);

modules/store/spec/store.spec.ts

@@ -26,6 +26,7 @@ import Spy = jasmine.Spy;
 import any = jasmine.any;
 import { skip, take } from 'rxjs/operators';
 import { MockStore, provideMockStore } from '../testing';
+import { createSelector } from '../src/selector';
 
 interface TestAppSchema {
   counter1: number;
@@ -448,10 +449,9 @@ describe('ngRx Store', () => {
 
   describe('Mock Store', () => {
     let mockStore: MockStore<TestAppSchema>;
+    const initialState = { counter1: 0, counter2: 1 };
 
     beforeEach(() => {
-      const initialState = { counter1: 0, counter2: 1 };
-
       TestBed.configureTestingModule({
         providers: [provideMockStore({ initialState })],
       });
@@ -482,6 +482,70 @@ describe('ngRx Store', () => {
         .subscribe(scannedAction => expect(scannedAction).toEqual(action));
       mockStore.dispatch(action);
     });
+
+    it('should allow mocking of store.select with string selector', () => {
+      const mockValue = 5;
+
+      mockStore.overrideSelector('counter1', mockValue);
+
+      mockStore
+        .select('counter1')
+        .subscribe(result => expect(result).toBe(mockValue));
+    });
+
+    it('should allow mocking of store.select with a memoized selector', () => {
+      const mockValue = 5;
+      const selector = createSelector(
+        () => initialState,
+        state => state.counter1
+      );
+
+      mockStore.overrideSelector(selector, mockValue);
+
+      mockStore
+        .select(selector)
+        .subscribe(result => expect(result).toBe(mockValue));
+    });
+
+    it('should allow mocking of store.pipe(select()) with a memoized selector', () => {
+      const mockValue = 5;
+      const selector = createSelector(
+        () => initialState,
+        state => state.counter2
+      );
+
+      mockStore.overrideSelector(selector, mockValue);
+
+      mockStore
+        .pipe(select(selector))
+        .subscribe(result => expect(result).toBe(mockValue));
+    });
+
+    it('should pass through unmocked selectors', () => {
+      const mockValue = 5;
+      const selector = createSelector(
+        () => initialState,
+        state => state.counter1
+      );
+      const selector2 = createSelector(
+        () => initialState,
+        state => state.counter2
+      );
+      const selector3 = createSelector(
+        selector,
+        selector2,
+        (sel1, sel2) => sel1 + sel2
+      );
+
+      mockStore.overrideSelector(selector, mockValue);
+
+      mockStore
+        .pipe(select(selector2))
+        .subscribe(result => expect(result).toBe(1));
+      mockStore
+        .pipe(select(selector3))
+        .subscribe(result => expect(result).toBe(6));
+    });
   });
 
   describe('Meta Reducers', () => {

modules/store/src/selector.ts

@@ -2,7 +2,11 @@ import { Selector, SelectorWithProps } from './models';
 
 export type AnyFn = (...args: any[]) => any;
 
-export type MemoizedProjection = { memoized: AnyFn; reset: () => void };
+export type MemoizedProjection = {
+  memoized: AnyFn;
+  reset: () => void;
+  setResult: (result?: any) => void;
+};
 
 export type MemoizeFn = (t: AnyFn) => MemoizedProjection;
 
@@ -12,12 +16,14 @@ export interface MemoizedSelector<State, Result>
   extends Selector<State, Result> {
   release(): void;
   projector: AnyFn;
+  setResult: (result?: Result) => void;
 }
 
 export interface MemoizedSelectorWithProps<State, Props, Result>
   extends SelectorWithProps<State, Props, Result> {
   release(): void;
   projector: AnyFn;
+  setResult: (result?: Result) => void;
 }
 
 export function isEqualCheck(a: any, b: any): boolean {
@@ -52,14 +58,24 @@ export function defaultMemoize(
   let lastArguments: null | IArguments = null;
   // tslint:disable-next-line:no-any anything could be the result.
   let lastResult: any = null;
+  let overrideResult: any;
 
   function reset() {
     lastArguments = null;
     lastResult = null;
+    overrideResult = undefined;
+  }
+
+  function setResult(result: any = undefined) {
+    overrideResult = result;
   }
 
   // tslint:disable-next-line:no-any anything could be the result.
   function memoized(): any {
+    if (overrideResult !== undefined) {
+      return overrideResult;
+    }
+
     if (!lastArguments) {
       lastResult = projectionFn.apply(null, arguments);
       lastArguments = arguments;
@@ -82,7 +98,7 @@ export function defaultMemoize(
     return newResult;
   }
 
-  return { memoized, reset };
+  return { memoized, reset, setResult };
 }
 
 export function createSelector<State, S1, Result>(
@@ -563,6 +579,7 @@ export function createSelectorFactory(
     return Object.assign(memoizedState.memoized, {
       release,
       projector: memoizedProjector.memoized,
+      setResult: memoizedState.setResult,
     });
   };
 }

modules/store/testing/src/mock_selector.ts

@@ -0,0 +1,11 @@
+import { MemoizedSelector, MemoizedSelectorWithProps } from '@ngrx/store';
+
+export interface MockSelector<State, Result>
+  extends MemoizedSelector<State, Result> {
+  setResult: (result?: Result) => void;
+}
+
+export interface MockSelectorWithProps<State, Props, Result>
+  extends MemoizedSelectorWithProps<State, Props, Result> {
+  setResult: (result?: Result) => void;
+}

modules/store/testing/src/mock_store.ts

@@ -6,11 +6,18 @@ import {
   INITIAL_STATE,
   ReducerManager,
   Store,
+  createSelector,
 } from '@ngrx/store';
 import { MockState } from './mock_state';
+import { MockSelector, MockSelectorWithProps } from './mock_selector';
 
 @Injectable()
 export class MockStore<T> extends Store<T> {
+  static selectors = new Map<
+    string | MockSelector<any, any> | MockSelectorWithProps<any, any, any>,
+    any
+  >();
+
   public scannedActions$: Observable<Action>;
 
   constructor(
@@ -20,6 +27,7 @@ export class MockStore<T> extends Store<T> {
     @Inject(INITIAL_STATE) private initialState: T
   ) {
     super(state$, actionsObserver, reducerManager);
+    this.resetSelectors();
     this.state$.next(this.initialState);
     this.scannedActions$ = actionsObserver.asObservable();
   }
@@ -28,6 +36,58 @@ export class MockStore<T> extends Store<T> {
     this.state$.next(nextState);
   }
 
+  overrideSelector<T, Result>(
+    selector: string,
+    value: Result
+  ): MockSelector<string, Result>;
+  overrideSelector<T, Result>(
+    selector: MockSelector<T, Result>,
+    value: Result
+  ): MockSelector<T, Result>;
+  overrideSelector<T, Result>(
+    selector: MockSelectorWithProps<T, any, Result>,
+    value: Result
+  ): MockSelectorWithProps<T, any, Result>;
+  overrideSelector<T, Result>(
+    selector:
+      | string
+      | MockSelector<any, any>
+      | MockSelectorWithProps<any, any, any>,
+    value: any
+  ) {
+    MockStore.selectors.set(selector, value);
+
+    if (typeof selector === 'string') {
+      const stringSelector = createSelector(() => {}, () => value);
+
+      return stringSelector;
+    }
+
+    selector.setResult(value);
+
+    return selector;
+  }
+
+  resetSelectors() {
+    MockStore.selectors.forEach((_, selector) => {
+      if (typeof selector !== 'string') {
+        selector.setResult();
+      }
+    });
+
+    MockStore.selectors.clear();
+  }
+
+  select(selector: any) {
+    if (MockStore.selectors.has(selector)) {
+      return new BehaviorSubject<any>(
+        MockStore.selectors.get(selector)
+      ).asObservable();
+    }
+
+    return super.select(selector);
+  }
+
   addReducer() {
     /* noop */
   }

modules/store/testing/src/testing.ts

@@ -6,6 +6,7 @@ import {
   ReducerManager,
   StateObservable,
   Store,
+  defaultMemoize,
 } from '@ngrx/store';
 import { MockStore } from './mock_store';
 import { MockReducerManager } from './mock_reducer_manager';
@@ -28,5 +29,6 @@ export function provideMockStore<T = any>(
 }
 
 export { MockReducerManager } from './mock_reducer_manager';
+export { MockSelector, MockSelectorWithProps } from './mock_selector';
 export { MockState } from './mock_state';
 export { MockStore } from './mock_store';

projects/example-app/src/app/auth/containers/__snapshots__/login-page.component.spec.ts.snap

@@ -4,7 +4,7 @@ exports[`Login Page should compile 1`] = `
 <bc-login-page
   error$={[Function Store]}
   pending$={[Function Store]}
-  store={[Function Store]}
+  store={[Function MockStore]}
 >
   <bc-login-form
     ng-reflect-pending="false"

projects/example-app/src/app/auth/containers/login-page.component.spec.ts

@@ -2,36 +2,36 @@ import { TestBed, ComponentFixture } from '@angular/core/testing';
 import { MatInputModule, MatCardModule } from '@angular/material';
 import { ReactiveFormsModule } from '@angular/forms';
 import { NoopAnimationsModule } from '@angular/platform-browser/animations';
-import { StoreModule, Store, combineReducers } from '@ngrx/store';
+import { Store } from '@ngrx/store';
 import { LoginPageComponent } from '@example-app/auth/containers/login-page.component';
 import { LoginFormComponent } from '@example-app/auth/components/login-form.component';
 import * as fromAuth from '@example-app/auth/reducers';
 import { LoginPageActions } from '@example-app/auth/actions';
+import { provideMockStore, MockStore } from '@ngrx/store/testing';
 
 describe('Login Page', () => {
   let fixture: ComponentFixture<LoginPageComponent>;
-  let store: Store<fromAuth.State>;
+  let store: MockStore<fromAuth.State>;
   let instance: LoginPageComponent;
 
   beforeEach(() => {
     TestBed.configureTestingModule({
       imports: [
         NoopAnimationsModule,
-        StoreModule.forRoot({
-          auth: combineReducers(fromAuth.reducers),
-        }),
         MatInputModule,
         MatCardModule,
         ReactiveFormsModule,
       ],
       declarations: [LoginPageComponent, LoginFormComponent],
+      providers: [provideMockStore()],
     });
 
     fixture = TestBed.createComponent(LoginPageComponent);
     instance = fixture.componentInstance;
     store = TestBed.get(Store);
+    store.overrideSelector(fromAuth.getLoginPagePending, false);
 
-    spyOn(store, 'dispatch').and.callThrough();
+    spyOn(store, 'dispatch');
   });
 
   /**