Angular: Test code in a module's constructor with NgMocks

Question

I have a simple notifications module that uses material's snack bar while listening on an Ngrx Selector. I dont have any components and work is done in the module's constructor so the consumer only needs to import the module and then dispatch a new notification.

@NgModule({
  declarations: [],
  imports: [
    CommonModule,
    StoreModule.forFeature(
      NOTIFICATIONS_STATE_FEATURE_KEY,
      notificationsModuleReducer
    ),
    MatSnackBarModule,
  ],
})
export class NotificationsModule {
  private store = inject(Store);
  private snackBar = inject(MatSnackBar);
  constructor() {
    this.store
      .select(selectNotifications)
      .pipe(debounceTime(1000))
      .subscribe((notification) => {
        if (notification) {
          const config = new MatSnackBarConfig();
          if (!notification.dontClose) {
            config.duration = 3000;
          }
          config.panelClass = [`${notification.kind}-notification`];
          this.snackBar.open(
            `${notification.kind.toUpperCase()}:  ${notification.message}`,
            'X',
            config
          );
        }
      });
  }
}

I need to write a test for coveragerage purpopses and I'm having trouble. I usually use NgMocks but I can live without it. I've tried to implement the method in Angular 5 testing code in module constructor but I continually get a null injector error for MatSnackBar.

it('opens the snack bar', () => {
  TestBed.configureTestingModule({
    imports: [NotificationsModule, MatSnackBarModule],
    providers: [provideMockStore()],
  })
    .compileComponents()
    .then(() => {
      const snackBar = TestBed.inject(MatSnackBar);
      const snackBarSpy = spyOn(snackBar, 'open').and.callThrough();
      const testConfig = new MatSnackBarConfig();
      testConfig.panelClass = [
        `${notificationTestState.notification?.kind}-notification`,
      ];

      expect(snackBarSpy).toHaveBeenCalledWith(
        notificationTestState.notification?.message as string,
        'X',
        testConfig
      );
    });
});

Error:

Unhandled promise rejection: NullInjectorError: R3InjectorError(CompilerModule)[MatSnackBar -> MatSnackBar]: NullInjectorError: No provider for MatSnackBar!

Any ideas?

Angular: Test code in a module's constructor with NgMocks

0 Answers0