Component TestBed

Custom test bed for testing Component.

info

Works for standalone and non-standalone component.

Quick example

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent) // 🛠️ Create the test bed which is re-compiled for each test
    .inject('prefs', Preferences); // 🖇️ Link a key to an injection for all tests, see below 👇

  it('should render title', tb(({ component, query }) => { // 🔋 Access enhanced tools for testing components 
    expect(component.title).toEqual('app-v17');
    const span = query.findElement('.content span');
    expect(span.textContent).toContain('app-v17 app is running!');
  }));

  it('should update preferences on click', tb(({ action, injected: { prefs } }) => { // 🤯 Retrieve injections by autocompletion
    expect(prefs.approved).toBeFalse();
    action.click('#my-button');
    expect(prefs.approved).toBeTrue();
  }));
});

componentTestBed(..)

Creates a specific test bed for component.

It returns a function to be used to wrap it's callback and from which you access tools (check ComponentTools).

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent);

  it('should ', tb((tools) => { // 👈 tb function used here
    // ... expectations
  }));
});

tb function supports the jasmine DoneFn and async/await notation.

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent);

  it('should ', tb(async (tools) => {
    // ... async expectations
  }));

  it('should ', tb((tools, done) => {
    // ... expectations
    done();
  }));
});

TestBed Options

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent, {} /* 👈 here */);

  it('should ', tb(() => {
    // ... expectations
  }));
});

imports

Default : []

Imports template's dependencies for the described component and its children.

note

It is often used for non-standalone component, because standalone component embed its own importations.

Example :

const tb = componentTestBed(AppComponent, {
  imports: [SharedModule, MaterialModule],
});

providers

Default : []

List of providers to be available during tests for the described component and its children.

Example :

const tb = componentTestBed(AppComponent, {
  providers: [AppService, { provide: StoreService, useClass: MockStoreService }],
});

declarations

Default : []

List of components, directives and pipes to be used in the described non-standalone component template.

Example :

const tb = componentTestBed(NonStandaloneComponent, {
  declarations: [ChildComponent, AppDirective, AppPipe],
});

schemas

Default : []

Allows specific elements and properties to be used in the template.

See Angular CUSTOM_ELEMENTS_SCHEMA and NO_ERRORS_SCHEMA.

Example :

const tb = componentTestBed(AppComponent, {
  schemas: [CUSTOM_ELEMENTS_SCHEMA],
});

noopAnimations

Default : true

Disable Angular animation.

note

It provides provideNoopAnimation() under the hood.

startDetectChanges

Default : true

Runs component fixture.detectChanges() before each assertion.

Has no effect if noTemplate is true.

noTemplate

Default : false

Useful when you only want to test the logic of the described component.

If enabled, no template will be rendered and no change detections will be performed.

httpTesting

Default : false

Enables HttpTestingTools.

verifyHttp

Default : true

When enabled, each assertion will end by HttpTestingController.verify().

warning

Works only if httpTesting is true, otherwise has no effect.

autoCompile

Default : true

Automatically compiles the custom test bed for each test.

checkCreate

Default : true

Automatically invokes the "should create" Angular test.

It checks if the provided described instance is truthy.

Assertion tools

The tb function provides ComponentTools.

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent);

  it('should ', tb((tools /* 👈 here */) => {
    // ... expectations
  }));
});

👉 ComponentTools extends BaseTools, RendererTools and HttpTestingTools.

component

The described component instance.

info

The instance is typed according to the passed component Type<T> in componentTestBed(..).

Example :

it('should ', tb(({ component }) => {
  expect(component.prop).toEqual('foo');
}));

Assertion options

For specific test, you enable/disable options that override the test bed options.

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent);

  it('should ', tb((tools) => {
    // ... expectations
  }, {} /* 👈 here */));
});

startDetectChanges

Same as options startDetectChanges but only for the current assertion.

verifyHttp

Same as options verifyHttp but only for the current assertion.

ComponentTestBed

import(..)

Same as options imports but with chaining methods.

Example :

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent)
    .import(SharedModule)
    .import([ThirdPartyModule, MaterialModule]);
});

provide(..)

Same as options providers but with chaining methods.

Example :

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent)
    .provide(AppService)
    .provide([StoreService, { provide: MY_TOKEN, useValue: mockValue }]);
});

declare(..)

Same as options declarations but with chaining methods.

Example :

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent)
    .declare(ChildComponent)
    .declare([HeaderComponent, AppPipe]);
});

inject(..)

Links an injected instance to a key and retrieve it into the enhanced tools by autocompletion.

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent)
    .inject('auth', AuthService);

  it('should ', tb(({ injected: { auth } }) => {
    // ... expectations
  }));
});

setup(..)

Setups extra action using the enhanced tools.

Works only for beforeEach and afterEach.

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent);

  beforeEach(tb.setup(({ component }) => {
    component.myInput = true;
  }));
});

compile()

To be used when you need to do third party setups before compiling the custom test bed.

warning

It has to be used into beforeEach(..) and autoCompile must be set to false.

describe('AppComponent', () => {
  const tb = componentTestBed(AppComponent, { autoCompile: false });

  beforeEach(async () => {
    // ... third party setup
    await tb.compile();
  });
});