shallow-with-effects

This is a small wrapper that allows unit-testing react components that use useEffect and useLayoutEffect using enzyme's shallow renderer.

It works by hooking into your test runner's lifecycle methods beforeEach and afterEach, and wrapping enzyne's shallow so that cleanup effects are handled upon unmount.

Out of the box support is provided for mocha and jest.

Usage example

Let's say we have a component that fetches the current user information when it is mounted.

Here's how we could test that, using shallow-with-effects with jest:

import React, { useEffect, useState } from 'react';
import shallowWithEffects from 'shallow-with-effects';
import { configure } from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

configure({ adapter: new Adapter() });

// wrap your tests with shallowWithEffects
// it handles cleaning up after itself
shallowWithEffects(shallow => {
  describe('CurrentUser', () => {
    it('fetches the current user when mounted', () => {
      let fetched = false
      // use the `shallow` function that is passed in rather than the version exported from enzyme
      // this allows you to test unmounting
      const rendered = shallow(<CurrentUser fetchCurrentUser={() => { fetched = true } />)
      expect(fetched).toEqual(true)
    })
  });
});

Thanks

Credit to mikeborozdin for the brilliant hack of using the effect function body as a key https://github.com/mikeborozdin/jest-react-hooks-shallow/blob/master/src/mock-use-effect/mock-use-effect.ts