javascript - How to mock React component methods with jest and enzyme

Question

I have a react component(this is simplified in order to demonstrate the issue):

class MyComponent extends Component {
    handleNameInput = (value) => {
        this.searchDish(value);
    };

    searchDish = (value) => {
      //Do something
    }

    render() {
        return(<div></div>)
    }
}

Now I want to test that handleNameInput() calls searchDish with the provided value.

In order to do this I would like to create a jest mock function that replaces the component method.

Here is my test case so far:

it('handleNameInput', () => {
   let wrapper = shallow(<MyComponent/>);
   wrapper.searchDish = jest.fn();
   wrapper.instance().handleNameInput('BoB');
   expect(wrapper.searchDish).toBeCalledWith('BoB');
})

But all I get in the console is SyntaxError:

SyntaxError

  at XMLHttpRequest.open (node_modules/jsdom/lib/jsdom/living/xmlhttprequest.js:458:15)
  at run_xhr (node_modules/browser-request/index.js:215:7)
  at request (node_modules/browser-request/index.js:179:10)
  at DishAdmin._this.searchDish (src/main/react/components/DishAdmin.js:155:68)
  at DishAdmin._this.handleNameInput (src/main/react/components/DishAdmin.js:94:45)
  at Object.<anonymous> (src/main/react/tests/DishAdmin.test.js:122:24)

So my question is, how do I properly mock component methods with enzyme?

Answer 1

The method can be mocked in this way:

it('handleNameInput', () => {
   let wrapper = shallow(<MyComponent/>);
   wrapper.instance().searchDish = jest.fn();
   wrapper.update();
   wrapper.instance().handleNameInput('BoB');
   expect(wrapper.instance().searchDish).toBeCalledWith('BoB');
})

You also need to call .update on the wrapper of the tested component in order to register the mock function properly.

The syntax error was coming from the wrong assingment (you need to assign the method to the instance). My other problems were coming from not calling .update() after mocking the method.