Jest mock DeviceEventEmitter from react-native

Issue

I am trying to mock DeviceEventEmitter from react-native using jest. The actual code adds and removes a listener on component mount and unmount respectively. I have tried a lot of solutions but none of them worked.

These are few ways which I tried to mock.

// type 1
jest.mock('react-native/Libraries/EventEmitter/RCTDeviceEventEmitter', () => {
  return {
     addListener: mockAddListener,
     remove: mockRemove
  }
});


// type 2
jest.mock('react-native/Libraries/EventEmitter/RCTDeviceEventEmitter', () => {
  const DeviceEventEmitter = jest.requireActual('react-native/Libraries/EventEmitter/RCTDeviceEventEmitter');
  return DeviceEventEmitter;
});

Any suggestions?

Solution

After a lot of experiment in trying to mock this, finally the below mock worked.

// Make sure you are using the right path for node_modules depending on your test file location
jest.mock('../../node_modules/react-native/Libraries/vendor/emitter/EventEmitter', () => {
    return class EventEmitter {
        emit = jest.fn()
        // Add other methods which ever you need to mock
    };
});

So basically DeviceEventEmitter extends EventEmitter. So mocking EventEmitter and implementing the required methods worked.

Answered By - Joshua