Angular unit test helpers and samples

_testing.md

Testing

Helpers and examples for unit testing on Angular applications and libraries.

activated-route-stub.ts

/* FILE TYPE: TEST HELPER */

// export for convenience.
export { ActivatedRoute } from '@angular/router';
import { convertToParamMap, Data, ParamMap, Params } from '@angular/router';
import { Observable, of, BehaviorSubject } from 'rxjs';

export interface ActivatedRouteSnapshotStub {
  data?: Data;
  paramMap?: ParamMap;
}

export interface ActivatedRouteProps {
  initialData?: Data;
  initialSnapshot?: ActivatedRouteSnapshotStub;
  initialParams?: Params;
}

export class ActivatedRouteStub {
  data: Observable<Data>;
  snapshot: ActivatedRouteSnapshotStub;
  readonly paramMap: Observable<ParamMap>;
  // ReplaySubject is not compatible with snapshot testing since it produces a window timestamp.
  private subject = new BehaviorSubject<ParamMap>(null);

  constructor(init: ActivatedRouteProps = {}) {
    this.paramMap = this.subject.asObservable();
    if (init.initialSnapshot) this.snapshot = init.initialSnapshot;
    if (init.initialData) {
      this.data = of(init.initialData);
      this.setParamMap(init.initialParams);
    }
  }

  setParamMap(params?: Params) {
    this.subject.next(convertToParamMap(params));
  }
}

component-suite.ts

/* FILE TYPE: TEST HELPER */

import { DebugElement } from '@angular/core';
import { ComponentFixture } from '@angular/core/testing';
import { By } from '@angular/platform-browser';

export interface ComponentSuiteElements<H, N = any> {
  host: ComponentTestingElement<H>;
  nested?: ComponentTestingElement<N>;
}

export interface ComponentTestingElement<T> {
  component: T;
  debugEl: DebugElement;
  nativeEl: Element | HTMLElement;
}

export class ComponentSuite<H, N = any> {
  elements: ComponentSuiteElements<H, N>;

  constructor(private fixture: ComponentFixture<H>, private selector?: string) {
    this.setElements();
  }

  private getHost(): ComponentTestingElement<H> {
    const component: H = this.fixture.componentInstance;
    const debugEl: DebugElement = this.fixture.debugElement;
    const nativeEl: Element | HTMLElement = debugEl.nativeElement;

    return { component, debugEl, nativeEl };
  }

  private getIntegrationElements(): ComponentSuiteElements<H, N> {
    const host: ComponentTestingElement<H> = this.getHost();
    const nested: ComponentTestingElement<N> = this.getNested(host.debugEl);

    return {
      host,
      nested
    };
  }

  private getNested(hostDebugEl: DebugElement): ComponentTestingElement<N> {
    const debugEl: DebugElement = hostDebugEl.query(By.css(this.selector));
    const component: N = debugEl.componentInstance;
    const nativeEl: Element | HTMLElement = debugEl.nativeElement;

    return { component, debugEl, nativeEl };
  }

  private getShallowElements(): ComponentSuiteElements<H> {
    return { host: this.getHost() };
  }

  private setElements(): void {
    if (this.selector) {
      this.elements = this.getIntegrationElements();
    } else {
      this.elements = this.getShallowElements();
    }
  }
}

http-client.spec.ts

/* FILE TYPE: HTTP TEST */

// Http testing module and mocking controller
import { HttpClient, HttpErrorResponse, HttpHeaders } from '@angular/common/http';
import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
// Other imports
import { TestBed } from '@angular/core/testing';

interface Data {
  name: string;
}

const testUrl = '/data';

describe('HttpClient testing', () => {
  let httpClient: HttpClient;
  let httpTestingController: HttpTestingController;

  beforeEach(() => {
    TestBed.configureTestingModule({
      imports: [HttpClientTestingModule]
    });

    // Inject the http service and test controller for each test
    httpClient = TestBed.get(HttpClient);
    httpTestingController = TestBed.get(HttpTestingController);
  });
  afterEach(() => {
    // After every test, assert that there are no more pending requests.
    httpTestingController.verify();
  });
  /// Tests begin ///
  it('can test HttpClient.get', () => {
    const testData: Data = { name: 'Test Data' };

    // Make an HTTP GET request
    httpClient.get<Data>(testUrl).subscribe(data =>
      // When observable resolves, result should match test data
      expect(data).toEqual(testData)
    );

    // The following `expectOne()` will match the request's URL.
    // If no requests or multiple requests matched that URL
    // `expectOne()` would throw.
    const req = httpTestingController.expectOne('/data');

    // Assert that the request is a GET.
    expect(req.request.method).toEqual('GET');

    // Respond with mock data, causing Observable to resolve.
    // Subscribe callback asserts that correct data was returned.
    req.flush(testData);
  });
  it('can test HttpClient.get with matching header', () => {
    const testData: Data = { name: 'Test Data' };

    // Make an HTTP GET request with specific header
    httpClient
      .get<Data>(testUrl, {
        headers: new HttpHeaders({ Authorization: 'my-auth-token' })
      })
      .subscribe(data => expect(data).toEqual(testData));

    // Find request with a predicate function.
    // Expect one request with an authorization header
    const req = httpTestingController.expectOne(r => r.headers.has('Authorization'));
    req.flush(testData);
  });

  it('can test multiple requests', () => {
    const testData: Data[] = [
      { name: 'bob' },
      { name: 'carol' },
      { name: 'ted' },
      { name: 'alice' }
    ];

    // Make three requests in a row
    httpClient.get<Data[]>(testUrl).subscribe(d => expect(d.length).toEqual(0));

    httpClient.get<Data[]>(testUrl).subscribe(d => expect(d).toEqual([testData[0]]));

    httpClient.get<Data[]>(testUrl).subscribe(d => expect(d).toEqual(testData));

    // get all pending requests that match the given URL
    const requests = httpTestingController.match(testUrl);
    expect(requests.length).toEqual(3);

    // Respond to each request with different results
    requests[0].flush([]);
    requests[1].flush([testData[0]]);
    requests[2].flush(testData);
  });

  it('can test for 404 error', () => {
    const emsg = 'deliberate 404 error';

    httpClient.get<Data[]>(testUrl).subscribe(
      data => fail('should have failed with the 404 error'),
      (error: HttpErrorResponse) => {
        expect(error.status).toEqual(404);
        expect(error.error).toEqual(emsg);
      }
    );

    const req = httpTestingController.expectOne(testUrl);

    // Respond with mock error
    req.flush(emsg, { status: 404, statusText: 'Not Found' });
  });

  it('can test for network error', () => {
    const emsg = 'simulated network error';

    httpClient.get<Data[]>(testUrl).subscribe(
      data => fail('should have failed with the network error'),
      (error: HttpErrorResponse) => {
        expect(error.error.message).toEqual(emsg);
      }
    );

    const req = httpTestingController.expectOne(testUrl);

    // Create mock ErrorEvent, raised when something goes wrong at the network level.
    // Connection timeout, DNS error, offline, etc
    const errorEvent = new ErrorEvent('so sad', {
      message: emsg,
      // The rest of this is optional and not used.
      // Just showing that you could provide this too.
      filename: 'HeroService.ts',
      lineno: 42,
      colno: 21
    });

    // Respond with mock error
    req.error(errorEvent);
  });

  it('httpTestingController.verify should fail if HTTP response not simulated', () => {
    // Sends request
    httpClient.get('some/api').subscribe();

    // verify() should fail because haven't handled the pending request.
    expect(() => httpTestingController.verify()).toThrow();

    // Now get and flush the request so that afterEach() doesn't fail
    const req = httpTestingController.expectOne('some/api');
    req.flush(null);
  });

  // Proves that verify in afterEach() really would catch error
  // if test doesn't simulate the HTTP response.
  //
  // Must disable this test because can't catch an error in an afterEach().
  // Uncomment if you want to confirm that afterEach() does the job.
  // it('afterEach() should fail when HTTP response not simulated',() => {
  //   // Sends request which is never handled by this test
  //   httpClient.get('some/api').subscribe();
  // });
});

page.ts

/* FILE TYPE: TEST HELPER */

import { Component, DebugElement } from '@angular/core';
import { By } from '@angular/platform-browser';
import { Router } from '@angular/router';

export class Page {
  private router: Router;

  constructor(
    private component: Component,
    private debugEl: DebugElement,
    private nativeEl: Element | HTMLElement
  ) {
    this.router = debugEl.injector.get(Router);
  }

  queryByAll<T>(): T[] {
    return <any>this.debugEl.query(By.all());
  }

  queryByCss<T>(selector: string): T {
    return <any>this.debugEl.query(By.css(selector));
  }

  queryAllByCss<T>(selector: string): T[] {
    return <any>this.debugEl.queryAll(By.css(selector));
  }

  queryByDirective<T>(directive: any): T {
    return <any>this.debugEl.query(By.directive(directive));
  }

  queryAllByDirective<T>(directive: any): T[] {
    return <any>this.debugEl.query(By.directive(directive));
  }

  spyOnMethod(method: string) {
    spyOn(this.component, <any>method);
  }

  spyOnMethodAndCallThrough(method: string) {
    spyOn(this.component, <any>method).and.callThrough();
  }
}

router-link-directive-stub.ts

/* FILE TYPE: TEST HELPER */

import { Directive, HostListener, Input, NgModule } from '@angular/core';

// export for convenience.
export { RouterLink } from '@angular/router';

/* tslint:disable:directive-class-suffix */
@Directive({
  selector: '[routerLink]'
})
export class RouterLinkStubDirective {
  navigatedTo: any = null;
  @Input()
  routerLink: any;
  @HostListener('click')
  onClick() {
    this.navigatedTo = this.routerLink;
  }
}

@NgModule({
  declarations: [RouterLinkStubDirective]
})
export class RouterStubsModule {}

sample.component.spec.ts

/* FILE TYPE: JEST COMPONENT TEST SAMPLE */

import { Component, DebugElement, Input } from '@angular/core';
import { ComponentFixture, TestBed, async } from '@angular/core/testing';
// Use Typescript path mapping to import test helpers.
import { CoreModule } from '@app/core/core.module';
import { Page } from '@testing';
import { ComponentSuite, ComponentSuiteElements } from '@testing';
import { cold, getTestScheduler } from 'jasmine-marbles';
import { of } from 'rxjs/observable/of';
import { MyAsyncService } from './my-async.service';
import { MyFromModuleService } from './my-from-module.service';
import { MyComponent } from './my.component';
import { MyService } from './my.service';

/* HERE YOUR STUBS AND MOCKS */
/*
  Use stub components for shallow testing.
  Do not use NO_ERRORS_SCHEMA.
*/
const optionsDataMock: Record<string, string> = {
  option1: 'option1',
  option2: 'option2',
  option3: 'option3',
};

@Component({ selector: 'pfx-child', template: '' })
class ChildStubComponent {
  @Input() prop: string;
}

@Injectable()
class MyAsyncServiceMock extends MyAsyncService {
  myAsyncServiceMethod: jest.Mock<Observable<any[]>> = jest.fn(() => of([]));
}

@Injectable()
class MyFromModuleServiceMock extends MyFromModuleService {
  observableMethod: jest.Mock<Observable<any[]>> = jest.fn(() => of([]));
  optionsObj: Record<string, string> = optionsDataMock;
  promiseMethod: jest.Mock<Promise<any[]>> = jest.fn(() => Promise.resolve([]));
  voidMethod: jest.Mock<void> = jest.fn();
}

/* HERE YOUR SUITES (describe) */
describe('MyComponent', () => {
  /* Declare all variables that you need for your specs. */
  let fixture: ComponentFixture<MyComponent>;
  let els: ComponentSuiteElements<MyComponent>;
  let page: Page;
  let myService: MyService;

  beforeEach(async(() => {
    // myAsyncServiceMethod = new myAsyncService().myAsyncServiceMethod; // OLD
    // myValue = 'myValue'; // OLD
    TestBed.configureTestingModule({
      imports: [CoreModule],
      declarations: [MyComponent, ChildStubComponent],
      providers: [MyService, { provide: MyAsyncService, useClass: MyAsyncServiceMock }]
    })
      .overrideComponent(MyComponent, {
        set: {
          providers: [{ provide: MyFromModuleService, useClass: MyFromModuleServiceMock }]
        }
      })
      .compileComponents()
      .then(() => {
        fixture = TestBed.createComponent(MyComponent);
        els = new ComponentSuite<MyComponent>(fixture).elements;
        /* User the Page class (or extend it) to encapsulate component's complexity. */
        page = new Page(component, debugEl, nativeEl);
        /* 
          We can also have non-mocked services here.
          For mocked services we directly test on their mocked methods.
        */
        myService = TestBed.inject(MyService);
      });
  }));

  /* HERE YOUR SPECS (it -> expect) */
  it('should create', () => {
    /*
      Detect changes on every spec and not on the beforeEach()
      since you might also want to check some logic on the component's constructor().
    */
    fixture.detectChanges();
    /* We use Jest snapshot testing instead of the usual matcher. */
    expect(fixture).toMatchSnapshot();
  });
  
  /* Shallow test example with ComponentSuite helper class */
  it('should generate as many titles as contents', () => {
    fixture.detectChanges();

    const titles: number = els.host.debugEl.queryAll(By.css('.title')).length;
    const contents: number = els.host.component.contents.toArray().length;

    expect(titles).toEqual(contents);
  });

  /* Work with jasmine marbles to test observables. */
  it('should test with jasmine marbles', () => {
    const q$ = cold('---x|', { x: myValue });
    myAsyncServiceMethod.and.returnValue(q$);

    fixture.detectChanges(); // ngOnInit()
    expect(els.host.nativeEl.textContent).toBe('...');

    getTestScheduler().flush(); // flush the observables

    fixture.detectChanges(); // update view
    expect(els.host.nativeEl.textContent).toBe(myValue);
  });
});

test-utils.ts

/* FILE TYPE: TEST HELPER */

/** Wait a tick, then detect changes */
export function advance(f: ComponentFixture<any>): void {
  tick();
  f.detectChanges();
}

/**
 * Create custom DOM event the old fashioned way
 *
 * https://developer.mozilla.org/en-US/docs/Web/API/Event/initEvent
 * Although officially deprecated, some browsers (phantom) don't accept the preferred "new Event(eventName)"
 */
export function newEvent(eventName: string, bubbles = false, cancelable = false) {
  const evt = document.createEvent('CustomEvent'); // MUST be 'CustomEvent'
  evt.initCustomEvent(eventName, bubbles, cancelable, null);
  return evt;
}

// See https://developer.mozilla.org/en-US/docs/Web/API/MouseEvent/button
/** Button events to pass to `DebugElement.triggerEventHandler` for RouterLink event handler */
export const ButtonClickEvents = {
  left: { button: 0 },
  right: { button: 2 }
};

/** Simulate element click. Defaults to mouse left-button click event. */
export function click(
  el: DebugElement | HTMLElement,
  eventObj: any = ButtonClickEvents.left
): void {
  if (el instanceof HTMLElement) {
    el.click();
  } else {
    el.triggerEventHandler('click', eventObj);
  }
}