active-enzyme

Boilerplate-free Enzyme testing.

Installation

$ npm install --save-dev active-enzyme

Enzyme is a great tool for performing tests on React components, especially using shallow rendering. This little library augments it with some niceties that allow you to easily lookup an element by className and save the resulting ShallowWrapper to a variable which is active--that is, it doesn't need to be requeried again after things change.

In a nutshell, a test such as this:

import React from 'react'
import { shallow } from 'enzyme'
import Greeting from './Greeting'
 
it('greets in multiple languages', () => {
  const name = 'John'
 
  const wrapper = shallow(<Greeting name={name} />)
 
  expect(wrapper.find('.greeting').text()).toBe(`Hello, ${name}!`)
 
  wrapper.find('.switchLanguage').simulate('click')
  expect(wrapper.find('.greeting').text()).toBe(`Bonjour, ${name}!`)
 
  wrapper.find('.switchLanguage').simulate('click')
  expect(wrapper.find('.greeting').text()).toBe(`Hello, ${name}!`)
})

can instead be written like this:

import React from 'react'
import { shallow } from 'active-enzyme'
import Greeting from './Greeting'
 
it('greets in multiple languages', () => {
  const name = 'John'
 
  const {
    greeting,
    switchLanguage 
  } = shallow(<Greeting name={name} />).classes
 
  expect(greeting.text()).toBe(`Hello, ${name}!`)
 
  switchLanguage.simulate('click')
  expect(greeting.text()).toBe(`Bonjour, ${name}!`)
 
  switchLanguage.simulate('click')
  expect(greeting.text()).toBe(`Hello, ${name}!`)
})

The two main features at work here are:

1. Enzyme wrapper objects acquire a special classes property which allows you to query based on a class names. This is nice because it allows you to use ES2015 destructuring syntax as above to select all the rendered elements you care about for a given test.
2. The first feature wouldn't be very useful with regular Enzyme if your test triggers re-renders of the element tree (as is happening here implicitly as a result of the 'click' events), because the greeting and switchLanguage wrappers are normally immutable. This library instead returns active wrappers, which change in response to the element tree being re-rendered.

Since the most common usage pattern is that you have a bunch of tests all testing the same component, there is a makeRenderer() utility which allows the individual tests to simply vary the props they're going to render it with:

import { makeRenderer } from 'active-enzyme'
import Greeting from './Greeting'
 
const render = makeRenderer(Greeting)
 
it('greets in multiple languages', () => {
  const name = 'John'
 
  const { greeting, switchLanguage } = render({ name }).classes
 
  expect(greeting.text()).toBe(`Hello, ${name}!`)
 
  switchLanguage.simulate('click')
  expect(greeting.text()).toBe(`Bonjour, ${name}!`)
 
  switchLanguage.simulate('click')
  expect(greeting.text()).toBe(`Hello, ${name}!`)
})

This has the nice added bonus that you no longer need to import React in your test suites!