How to correctly mock an ES6 class in Jest?

General Discussions
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3

Great approach, But if you want a cleaner way to mock without implementing custom functions inside the test, you can mock return values directly using jest.mock().

This makes the setup reusable across multiple tests:

jest.mock('mailgun-js');
import mailgun from 'mailgun-js';
import Mailer from '../../../../server/services/emails/mailer';

mailgun.mockReturnValue({
  messages: () => ({
    send: jest.fn().mockImplementation((args, callback) => callback())
  })
});

Now, the test becomes much simpler:

test('successful email send', async () => {
  const result = await Mailer.send('to@example.com', 'Subject', 'Body');
  expect(result).toBe('The email was sent successfully!');
});

This approach makes your jest mock class setup much cleaner while keeping the focus on testing. :white_check_mark: