Epic unit tests with TypeScript, Redux, RxJS 6 and Jest

unicorn.epic.test.ts

// src/tests/unicorn/unicorn.epic.test.ts

import { ActionsObservable } from 'redux-observable';
import { of, throwError } from 'rxjs';
import { toArray } from 'rxjs/operators';
import UnicornActions from '../../store/unicorn/unicorn.action';
import UnicornApiService from '../../store/unicorn/unicorn.api.service';
import UnicornEpics from '../../store/unicorn/unicorn.epic';

describe('Unicorn test', () => {
  describe('getUnicorn', () => {
    test('send correct actions when success', (done) => {
      const response = {data: {id: '1', name: 'My awesome Unicorn!'}};

      jest.spyOn(UnicornApiService, 'getUnicorn')
        .mockImplementation(() => of(response));

      const expected = UnicornActions.done(response, UnicornActions.Types.GET_UNICORN);

      const action$ = ActionsObservable.of(
        UnicornActions.getUnicorn('1')
      );

      UnicornEpics.getUnicorn(action$)
        .subscribe((actual: any) => {
            expect(actual).toEqual(expected);
            done();
          }
        );
    });

    test('send correct actions when error', (done) => {
      const error = {error: 'Error'};

      jest.spyOn(UnicornApiService, 'getUnicorn')
        .mockImplementation(() => throwError(error));

      const expected = UnicornActions.error(error, UnicornActions.Types.GET_UNICORN);

      const action$ = ActionsObservable.of(
        UnicornActions.getUnicorn('99')
      );

      UnicornEpics.getUnicorn(action$)
        .subscribe((actual: any) => {
            expect(actual).toEqual(expected);
            done();
          }
        );
    });
  });

  describe('likeUnicorn', () => {
    // Multiple actions example
    test('send correct actions when success', (done) => {
      const response = {data: {id: '1', name: 'My awesome Unicorn!', likeCount: 1}};

      jest.spyOn(UnicornApiService, 'likeUnicorn')
        .mockImplementation(() => of(response));

      const expected = [
        UnicornActions.done(response, UnicornActions.Types.LIKE_UNICORN),
        UnicornActions.updateUnicorn('1', {color: 'rainbow'})
      ];

      const action$ = ActionsObservable.of(
        UnicornActions.likeUnicorn('1')
      );

      UnicornEpics.likeUnicorn(action$)
        .pipe(toArray()) // IMPORTANT: To get all the actions
        .subscribe((actual: any) => {
            expect(actual).toEqual(expected);
            done();
          }
        );
    });

    test('send correct actions when error', (done) => {
      const error = {error: 'Error'};

      jest.spyOn(UnicornApiService, 'likeUnicorn')
        .mockImplementation(() => throwError(error));

      const expected = UnicornActions.error(error, UnicornActions.Types.LIKE_UNICORN);

      const action$ = ActionsObservable.of(
        UnicornActions.likeUnicorn('1')
      );

      UnicornEpics.likeUnicorn(action$)
        .subscribe((actual: any) => {
            expect(actual).toEqual(expected);
            done();
          }
        );
    });
  });

  describe('updateUnicorn', () => {
    test('send correct actions when success', (done) => {
      const response = {data: {id: '1', name: 'My awesome Unicorn!', likeCount: 1, color: 'blue'}};

      jest.spyOn(UnicornApiService, 'updateUnicorn')
        .mockImplementation(() => of(response));

      const expected = UnicornActions.done(response, UnicornActions.Types.UPDATE_UNICORN);

      const action$ = ActionsObservable.of(
        UnicornActions.updateUnicorn('1', {color: 'blue'})
      );

      UnicornEpics.updateUnicorn(action$)
        .subscribe((actual: any) => {
            expect(actual).toEqual(expected);
            done();
          }
        );
    });

    test('send correct actions when error', (done) => {
      const error = {error: 'Error'};

      jest.spyOn(UnicornApiService, 'updateUnicorn')
        .mockImplementation(() => throwError(error));

      const expected = UnicornActions.error(error, UnicornActions.Types.UPDATE_UNICORN);

      const action$ = ActionsObservable.of(
        UnicornActions.updateUnicorn('1', {color: 'blue'})
      );

      UnicornEpics.updateUnicorn(action$)
        .subscribe((actual: any) => {
            expect(actual).toEqual(expected);
            done();
          }
        );
    });
  });
});