Question: How can I test BullMQ jobs with Jest in Node.js?

Answer

To test BullMQ jobs with Jest in Node.js, you need to follow these steps:

1. Set up Jest in your project: First, make sure Jest is installed and configured properly in your project. If not, you can add it using npm or yarn:

npm install --save-dev jest

or

yarn add --dev jest

2. Create BullMQ Jobs: Let's assume you have a simple BullMQ job called sendEmail:

const Queue = require('bullmq').Queue;
const sendEmailQueue = new Queue('sendEmail');

sendEmailQueue.add('send', { email: 'test@example.com', message: 'Hello!' });

3. Mock BullMQ: Because we don't want to actually send emails when running tests, use Jest to mock the BullMQ functionality. Here's how to do that:

jest.mock('bullmq', () => {
  return {
    Queue: jest.fn().mockImplementation(() => {
      return {
        add: jest.fn()
      };
    })
  };
});

4. Write Tests: Now, you can write a test for any function that uses the sendEmail queue. If the function calls sendEmailQueue.add(), the mock implementation will be used instead of the real one:

const { sendEmail } = require('./sendEmail');
const { Queue } = require('bullmq');

test('sendEmail function should add a job to the queue', async () => {
  await sendEmail('test@test.com', 'Hello!');

  expect(Queue.mock.instances[0].add).toHaveBeenCalledWith('send', { email: 'test@test.com', message: 'Hello!' });
});

Remember, this is a basic example. In a real-world scenario, you might have more complex jobs and may need to adjust your mocks accordingly.