test(store-testing): nextMock and spyOnDispatcher tests

modules/store/spec/store.spec.ts

@@ -20,6 +20,7 @@ import {
 import Spy = jasmine.Spy;
 import any = jasmine.any;
 import { take } from 'rxjs/operators';
+import { MockStore, provideMockStore } from '../testing';
 
 interface TestAppSchema {
   counter1: number;
@@ -432,4 +433,47 @@ describe('ngRx Store', () => {
       };
     }
   });
+
+  describe('State mocking', () => {
+    let mockStore: MockStore<TestAppSchema>;
+    beforeEach(() => {
+      const initialState = { counter1: 0, counter2: 1 };
+      const reducers = {
+        counter1: counterReducer,
+        counter2: counterReducer,
+        counter3: counterReducer,
+      };
+
+      TestBed.configureTestingModule({
+        imports: [StoreModule.forRoot(reducers, { initialState })],
+        providers: [provideMockStore()],
+      });
+
+      mockStore = TestBed.get(Store);
+    });
+
+    it('should set the initial state to a mocked one', (done: DoneFn) => {
+      const fixedState = {
+        counter1: 17,
+        counter2: 11,
+        counter3: 25,
+      };
+      mockStore.nextMock(fixedState);
+      mockStore.pipe(take(1)).subscribe({
+        next(val) {
+          expect(val).toEqual(fixedState);
+        },
+        error: done.fail,
+        complete: done,
+      });
+    });
+
+    it('should set a spy on dispatcher', () => {
+      const spyFactory = () => jasmine.createSpy('dispatcher');
+      const action = { type: INCREMENT };
+      mockStore.spyOnDispatch(spyFactory);
+      mockStore.dispatch(action);
+      expect(mockStore.dispatch).toHaveBeenCalledWith(action);
+    });
+  });
 });

modules/store/testing/src/testing.ts

@@ -20,9 +20,13 @@ export class MockStore<T> extends Store<T> {
     this.source = this.stateSubject.asObservable();
   }
 
-  nextMock(nextState: T) {
+  nextMock(nextState: T): void {
     this.stateSubject.next(nextState);
   }
+
+  spyOnDispatch(spyFactory: Function): void {
+    this.dispatch = spyFactory(this.dispatch);
+  }
 }
 
 export function provideMockStore() {