使用 Jest 对 HttpInterceptor 进行单元测试

Question

Need help to write unit test for the the below scenario:

HttpInterceptor code

import {
  HttpEvent,
  HttpHandler,
  HttpInterceptor,
  HttpRequest
} from '@angular/common/http';
import { Injectable } from '@angular/core';
import { catchError, Observable, throwError } from 'rxjs';
import { UnauthorizedErrorDialogComponent } from 'src/app/shared/components/unauthorized-error-dialog/unauthorized-error-dialog.component';
import { SvDialogService } from 'sv-shared-library';

@Injectable({
  providedIn: 'root'
})
export class GlobalErrorIntercepterService
  implements HttpInterceptor
{
  constructor(private dialog: SvDialogService) {}

  intercept(
    req: HttpRequest<any>,
    next: HttpHandler
  ): Observable<HttpEvent<any>> {
    return next.handle(req).pipe(
      catchError((err) => {
        console.log(err);
        if (err.status === 401) {
          this.dialog.open(UnauthorizedErrorDialogComponent);
        }
        return throwError(() => new Error(err));
      })
    );
  }
}

Test Cases:-

1. If the error status is 401 the dialog box should open
2. If the error status is not 401 if should throw error

Answer 1

beforeEach(() => {
TestBed.configureTestingModule({
  imports: [HttpClientTestingModule, SharedModule],
  providers: [
    { provide: SvDialogService, useValue: dialogContext },
    {
      provide: HTTP_INTERCEPTORS,
      useClass: GlobalErrorIntercepterService,
      multi: true
    },
    {
      provide: SvDialogService,
      useValue: autoSpy(SvDialogService)
    }
  ]
}).compileComponents();

dialogContext = TestBed.inject(SvDialogService);
http = TestBed.inject(HttpClient);
httpMock = TestBed.inject(HttpTestingController);
service = TestBed.inject(GlobalErrorIntercepterService);});

it('Http Error 401', () => {
const url = 'https://www.google.com/';
const mockHandler = {
  handle: jest.fn(() =>
    throwError(
      new HttpErrorResponse({
        status: 401,
        error: { message: 'Unauthorized' }
      })
    )
  )
};

const req = new HttpRequest('GET', url, {
  reportProgress: true
});

service.intercept(req, mockHandler).subscribe({
  next: (response) => {
    fail('Expected error');
  },
  error: (err) => {
    expect(err).toBeTruthy();
    expect(dialogContext.open).toBeCalled();
  },
  complete: () => {}
}); });