import { spy } from 'sinon';
import { shallow } from 'enzyme';

// Utility method to asynchronously wait for component's willMount function to
// complete. Requires the componentWillMount method *returns* its async promise
// to wait for
export const willMount = async unmountedComponent => {
  // Spy on the willmount method
  const lifecycleMethod = spy(unmountedComponent.type.prototype, 'componentWillMount');
  const wrapper = shallow(unmountedComponent);

  // Wait for the return value of the spy (the promise returned in
  // componentWillMount) and then undo the mock
  await lifecycleMethod.returnValues[0];
  lifecycleMethod.restore();

  // Update component so async changes take place
  return wrapper.update();
};