Mock components, services and more out of annoying dependencies in Angular tests

ng-mocks is a testing library which helps with mocking services, components, directives, pipes and modules in tests for Angular applications. When we have a noisy child component, or any other annoying dependency, ng-mocks has tools to turn these declarations into their mocks, keeping interfaces as they are, but suppressing their implementation.

The current version of ng-mocks has been tested and can be used with:

Angular	ng-mocks	Jasmine	Jest	Ivy
18	latest	yes	yes	yes
17	latest	yes	yes	yes
16	latest	yes	yes	yes
15	latest	yes	yes	yes
14	latest	yes	yes	yes
13	latest	yes	yes	yes
12	latest	yes	yes	yes
11	latest	yes	yes	yes
10	latest	yes	yes	yes
9	latest	yes	yes	yes
8	latest	yes	yes
7	latest	yes	yes
6	latest	yes	yes
5	latest	yes	yes

In the header menu we can find preconfigured sandboxes, where we could check all the features. To focus on a particular one, simply prefix it with fdescribe or fit.

Also, there is a brief summary with the latest changes in CHANGELOG.

Quick Navigation

• How to read this manual
• Making tests faster
• Auto-spy everything
• Testing inputs, outputs and lifecycle hooks
• Mocking methods in components before their initialization

Very short introduction

Global configuration for mocks in src/test.ts. In case of jest src/setup-jest.ts / src/test-setup.ts should be used.

src/test.ts

// All methods in mock declarations and providers
// will be automatically spied on their creation.
// https://ng-mocks.sudo.eu/extra/auto-spy
ngMocks.autoSpy('jasmine'); // or jest

// ngMocks.defaultMock helps to customize mocks
// globally. Therefore, we can avoid copy-pasting
// among tests.
// https://ng-mocks.sudo.eu/api/ngMocks/defaultMock
ngMocks.defaultMock(AuthService, () => ({
  isLoggedIn$: EMPTY,
  currentUser$: EMPTY,
}));

An example of a spec for a profile edit component.

src/profile.component.spec.ts

// Let's imagine that there is a ProfileComponent
// and it has 3 text fields: email, firstName,
// lastName, and a user can edit them.
// In the following test suite, we would like to
// cover behavior of the component.
describe('profile:builder', () => {
  // Helps to reset customizations after each test.
  // Alternatively, you can enable
  // automatic resetting in test.ts.
  MockInstance.scope();

  // Let's configure TestBed via MockBuilder.
  // The code below says to mock everything in
  // ProfileModule except ProfileComponent and
  // ReactiveFormsModule.
  beforeEach(() => {
    // The result of MockBuilder should be returned.
    // https://ng-mocks.sudo.eu/api/MockBuilder
    return MockBuilder(ProfileComponent, ProfileModule)
      .keep(ReactiveFormsModule);
    // // or old fashion way
    // return TestBed.configureTestingModule({
    //   imports: [
    //     MockModule(SharedModule), // mock
    //     ReactiveFormsModule, // real
    //   ],
    //   declarations: [
    //     ProfileComponent, // real
    //     MockPipe(CurrencyPipe), // mock
    //     MockDirective(HoverDirective), // mock
    //   ],
    //   providers: [
    //     MockProvider(AuthService), // mock
    //   ],
    // }).compileComponents();
  });

  // A test to ensure that ProfileComponent
  // can be created.
  it('should be created', () => {
    // MockRender is an advanced version of
    // TestBed.createComponent.
    // It respects all lifecycle hooks,
    // onPush change detection, and creates a
    // wrapper component with a template like
    // <app-root ...allInputs></profile>
    // and renders it.
    // It also respects all lifecycle hooks.
    // https://ng-mocks.sudo.eu/api/MockRender
    const fixture = MockRender(ProfileComponent);

    expect(fixture.point.componentInstance).toEqual(
      assertion.any(ProfileComponent),
    );
  });

  // A test to ensure that the component listens
  // on ctrl+s hotkey.
  it('saves on ctrl+s hot key', () => {
    // A fake profile.
    const profile = {
      email: '[email protected]',
      firstName: 'testFirst2',
      lastName: 'testLast2',
    };

    // A spy to track save calls.
    // MockInstance helps to configure mock
    // providers, declarations and modules
    // before their initialization and usage.
    // https://ng-mocks.sudo.eu/api/MockInstance
    const spySave = MockInstance(
      StorageService,
      'save',
      jasmine.createSpy(), // or jest.fn()
    );

    // Renders <profile [profile]="params.profile">
    // </profile>.
    // https://ng-mocks.sudo.eu/api/MockRender
    const { point } = MockRender(
      ProfileComponent,
      { profile }, // bindings
    );

    // Let's change the value of the form control
    // for email addresses with a random value.
    // ngMocks.change finds a related control
    // value accessor and updates it properly.
    // https://ng-mocks.sudo.eu/api/ngMocks/change
    ngMocks.change(
      '[name=email]', // css selector
      '[email protected]', // an email address
    );

    // Let's ensure that nothing has been called.
    expect(spySave).not.toHaveBeenCalled();

    // Let's assume that there is a host listener
    // for a keyboard combination of ctrl+s,
    // and we want to trigger it.
    // ngMocks.trigger helps to emit events via
    // simple interface.
    // https://ng-mocks.sudo.eu/api/ngMocks/trigger
    ngMocks.trigger(point, 'keyup.control.s');

    // The spy should be called with the user
    // and the random email address.
    expect(spySave).toHaveBeenCalledWith({
      email: '[email protected]',
      firstName: profile.firstName,
      lastName: profile.lastName,
    });
  });
});

Extra

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Thank you!

P.S. Feel free to contact us if you need help.