1. in the whole describe() lambda function, define below handles that can be referenced in all tests.
// use SpyObj because we want to spy multiple methods of the object
const testStore = jasmine.createSpyObj('Store', ['select', 'dispatch', 'pipe']);
// used to mock receving dispatched action
const actions$: ReplaySubject<any> = new ReplaySubject();
let fixture : ComponentFixture<CurrentComponent>;
let component: CurrentComponent;
2. both sync and async version of beforeEach happens before It()
beforeEach(async(() => {
......
TestBed.configureTestingModule({ declarations: [XComponent, YComponent, ......], providers: [XService, YService, // normal injection provideMockActions(() => actions$),
{ provide: Store, useValue: testStore },
]
})
.compileComponents(); //compileComponents is async method
}));
beforeEach(()=>{
testStore.dispatch.and.returnValue(true);
testStore.select.and.callFake(()=>Observable.of(false));
testStore.pipe.and.callFake(()=>Observable.of(true));
// the store just gave some random objects so component won't throw exception
fixture = TestBed.createComponent(CurrentComponent);
component = fixture.componentInstance;
});
3. the tests Itself
It('some test', ()=> {
action$.next({type: '[Action Name] Action Description', payload: { success: true}
}); // mocking the component getting an action from the store.
component.someField = true; // because we called faked "select" and "pipe" spy methods, so we have to manually do the job.
fixture.detectChanges();
const compiled = fixture.debugElement.nativeElement;
expect(compile.querySelector(".elementId")).toBeTruthy();
expect(testStore.dispatch).toHaveBeenCalledWith(new SomeAction(...));
});
the drawback of this method is “component.someField = true;”, this is NOT really testing the NGRX action pipe/select and subscription method content.
to fix that, “testStore.select.and.callFake(()=>Observable.of(false));” need to change to fake something that will really fit and be passed to the subscription method. like
()=>Observable.of({the projection of appState});