jest-glamor-react

Jest utilities for Glamor and React

The problem

If you use glamor as your CSS-in-JS solution, and you use snapshot testing with jest then you probably have some test snapshots that look like:

<h1
  class="css-1tnuino"
>
  Hello World
</h1>

And that's not super helpful from a styling perspective. Especially when there are changes to the class, you can see that it changed, but you have to look through the code to know what caused the class name to change.

This solution

This allows your snapshots to look more like:

.css-1tnuino,
[data-css-1tnuino] {
  font-size: 1.5em;
  text-align: center;
  color: palevioletred;
}

<h1
  class="css-1tnuino"
>
  Hello World
</h1>

This is much more helpful because now you can see the CSS applied and over time it becomes even more helpful to see how that changes over time.

This builds on the work from @MicheleBertoli in jest-styled-components to bring a similar experience to React projects that use glamor.

Preview

Installation

This module is distributed via npm which is bundled with node and should be installed as one of your project's devDependencies:

npm install --save-dev jest-glamor-react

Usage

At the top of your test file:

import serializer from 'jest-glamor-react'

expect.addSnapshotSerializer(serializer)

Or in your Jest serializer config:

{
  "snapshotSerializers": [
    "jest-glamor-react"
  ]
}

If you have set jest.config variable "testEnvironment": "node", you will need to manually mock up browser gloabl objects so it is recommended to use "testEnvironment": "jsdom" instead.

Here are some components:

import React from 'react'
import * as glamor from 'glamor'

function Wrapper(props) {
  const className = glamor.css({
    padding: '4em',
    background: 'papayawhip',
  })
  return <section className={`${className}`} {...props} />
}

function Title(props) {
  const className = glamor.css({
    fontSize: '1.5em',
    textAlign: 'center',
    color: 'palevioletred',
  })
  return <h1 className={`${className}`} {...props} />
}

And here's how we'd test them with react-test-renderer:

import React from 'react'
import renderer from 'react-test-renderer'

test('react-test-renderer', () => {
  const tree = renderer
    .create(
      <Wrapper>
        <Title>Hello World, this is my first glamor styled component!</Title>
      </Wrapper>,
    )
    .toJSON()

  expect(tree).toMatchSnapshot()
})

Works with enzyme too:

import * as enzyme from 'enzyme'
import toJson from 'enzyme-to-json'

test('enzyme', () => {
  const ui = (
    <Wrapper>
      <Title>Hello World, this is my first glamor styled component!</Title>
    </Wrapper>
  )

  expect(toJson(enzyme.shallow(ui))).toMatchSnapshot(`enzyme.shallow`)
  expect(toJson(enzyme.mount(ui))).toMatchSnapshot(`enzyme.mount`)
  expect(toJson(enzyme.render(ui))).toMatchSnapshot(`enzyme.render`)
})

If you use a library with a similar stylesheet solution to glamor like cxs you can do this instead:

import {sheet} from 'cxs'
import serializer from 'jest-glamor-react'

expect.addSnapshotSerializer(serializer(sheet))

You can also pass custom class name replacer to serializer function:

import {sheet} from 'cxs'
import serializer from 'jest-glamor-react'

function replaceClassNames(className, index) {
  return `my-class-name-${index}`
}

expect.addSnapshotSerializer(serializer(sheet, replaceClassNames))

Class name replacer will receive original class name and class name index

Then you can create components like this:

import React from 'react'
import cxs from 'cxs'

function Wrapper(props) {
  const className = cxs({
    padding: '4em',
    background: 'papayawhip',
  })
  return <section className={`${className}`} {...props} />
}

function Title(props) {
  const className = cxs({
    fontSize: '1.5em',
    textAlign: 'center',
    color: 'palevioletred',
  })
  return <h1 className={`${className}`} {...props} />
}

And test them the same way as before.

Inspiration

As mentioned earlier, @MicheleBertoli's jest-styled-components was a huge inspiration for this project. And much of the original code came from from that MIT Licensed project. Thank you so much Michele! 👏