NestJS Bull Queues: How to skip processing in test env?

Question

I'm using NestJS Queues via Bull and writing unit tests in Jest. I want to skip the processing of jobs triggered during testing.

There's a GH issue on test mode for Bull but they won't implement it.

Preferably I'd avoid extensive mocking, a simple option on BullModule would be best.

Answer 1

I also had a hard time with this, so I'm posting my solution. I'm just simplifying my code for this purpose, so use with caution, there might be some typos etc.

describe('JobCreatorService', () => {
  let service: JobCreatorService;
  let moduleRef: TestingModule;

  const exampleQueueMock = { add: jest.fn() };

  beforeEach(async () => {
    jest.resetAllMocks();
    moduleRef = await Test.createTestingModule({
      imports: [
        BullModule.registerQueue({
          name: EXAMPLE_QUEUE,
        }),
      ],
    })
      .overrideProvider(getQueueToken(EXAMPLE_QUEUE))
      .useValue(exampleQueueMock)
      .compile();

    service = moduleRef.get<JobCreatorService>(JobCreatorService);
  });

  afterAll(async () => {
    await moduleRef.close();
  });

  it('should dispatch job', async () => {
    await service.methodThatDispatches();
    expect(exampleQueueMock.add).toHaveBeenCalledWith({example: jobData});
  });
});

I don't recommend unit tests having side effects - like storing data in the DB or redis, that's why this approach. However if you prefer to actually store the jobs in redis, you might find some inspiration here: https://github.com/nestjs/bull/blob/master/e2e/module.e2e-spec.ts