How to spy componentWillMount using jest and enzyme

Question

I am trying to test whether componentWillMount was called and for that my test is

test(\'calls `componentWillMount` before rendering\', () => {
  let fn =         


        

Answer 1

Try this:

test('calls `componentWillMount` before rendering', () => {
  const onWillMount = jest.fn();
  SomeComponent.prototype.componentWillMount = onWillMount;
  mount();

  expect(onWillMount).toBeCalled();
});