React Jest Testing onSubmit

Question

I am new to react and jest. I have been looking everywhere for testing but I cannot find anything that is helpful. This is partially because I am so new to it, I havent a clue where to start. So bear with me, please.

I have an add to cart file which renders a form with a button inside it. The button is another component, so I'm not looking to test it. I have to test the onSubmit function for the form. Any thoughts? References?

Here is my code so far for the test:

describe('AddToCart', () => {
  const React = require('react');
  const BaseRenderer = require('react/lib/ReactTestUtils');
  const Renderer = BaseRenderer.createRenderer();
  const ReactTestUtils = require('react-addons-test-utils');
  const AddToCart = require('../index.js').BaseAddToCart;

  it('Will Submit', () => {
    formInstance = ReactTestUtils.renderIntoDocument(<AddToCart product="" quantity=""/>);
    expect(ReactTestUtils.Simulate.onSubmit(formInstance)).toBeCalled();
  });
});

I'm getting this error:

Invariant Violation: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined.

Answer 1

Consider using Jest with Enzyme. I think it's good stack for unit testing in react.

Also, I made a sample test that tests onSubmit function in LogIn component.

import React from 'react';
import {shallow} from 'enzyme';
import LogIn from './LogIn';

describe('<LogIn />', () => {
    const testValues = {
        username: 'FOO',
        password: 'BAZ',
        handleSubmit: jest.fn(),
    };

    it('Submit works', () => {

        const component = shallow(
            <LogIn {...testValues} />
        );
        component.find('#submitButton').simulate('click');
        expect(testValues.handleSubmit).toHaveBeenCalledTimes(1);
        expect(testValues.handleSubmit).toBeCalledWith({username: testValues.username, password: testValues.password});
    });
});