Exploring the use of .pipe with Angular Jest for testing

Currently, I am trying to test the following .ts file:

create(entityResourceID, params: any): Observable <any>{
        const url = `${this.apiUrl}/${entityResourceID}/assignee`;
        return this.http.post(url, params).pipe(
            map(() => { this.toaster.success('Successfully Asssigned Email'); }),
            catchError((error) => [
              console.error(error),
              this.toaster.error('Failed Assigning Email')
            ])
          );
        }
    

However, I encountered an error stating that .pipe is not a function

Here is my current test spec.ts file setup:

describe('create', () => {
        it('should return a valid url', () => {
            const spy = jest.spyOn(mockHttpClient, 'post').mockReturnValue('test');
            const result = component.create(testEntityID, {});
            expect(spy).toBeCalledWith('entities/url/assignee', {});
            expect(result).toStrictEqual('test');
        });
    });
    

I am aware that testing has become challenging because of the return type being an Observable. Can anyone guide me on how I can return an Observable from my spy in order to efficiently test both cases?

Answer №1

The issue here arises from the fact that you are simulating the post method by returning a string value instead of an Observable containing your desired value. If you are familiar with rxjs, you can solve this problem by following these steps...

import { of } from 'rxjs';

const spy = jest.spyOn(mockHttpClient,'post').mockReturnValue(of('test'));

The of method serves as a simplified version of Obeservable.of(yourValueHere)

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