jest-serializer-html

What is jest-serializer-html?

The jest-serializer-html package is a Jest serializer for HTML strings. It helps in making HTML snapshots more readable and easier to debug by formatting the HTML content in a more human-readable way.

What are jest-serializer-html's main functionalities?

HTML Serialization

This feature allows you to serialize HTML strings in your Jest tests. By adding the serializer, your HTML snapshots will be formatted in a more readable way, making it easier to identify changes and debug issues.

const serializer = require('jest-serializer-html');
expect.addSnapshotSerializer(serializer);

Customizing Serialization

This feature allows you to customize the serialization process. For example, you can collapse whitespace in the HTML output to make the snapshots more compact.

const serializer = require('jest-serializer-html');
expect.addSnapshotSerializer(serializer({ collapseWhitespace: true }));

Other packages similar to jest-serializer-html

jest-serializer

jest-serializer is a general-purpose serializer for Jest. It allows you to create custom serializers for various data types, including HTML. While it is more flexible, it requires more setup compared to jest-serializer-html, which is specifically designed for HTML.

pretty-format

pretty-format is a package used by Jest internally to format various data types, including HTML. It provides a more general solution for formatting data in Jest snapshots, but it may not be as specialized or straightforward for HTML as jest-serializer-html.

jest-html

jest-html is another package that provides utilities for testing HTML with Jest. It includes matchers and serializers for HTML, offering a more comprehensive solution for HTML testing compared to jest-serializer-html, which focuses solely on serialization.

README

A Jest snapshot serializer that beautifies HTML.

When using this Jest serializer, it will turn any string starting with '<' to nicely indented HTML in the snapshot.

This serializer is based on diffable-html which is an opinionated HTML formatter that will ease readability of diffs in case of failing snapshot tests.

Install

Add the package as a dev-dependency:

# With npm
npm install --save-dev jest-serializer-html

# With yarn
yarn add --dev jest-serializer-html

Update package.json to let Jest know about the serializer:

"jest": {
  "snapshotSerializers": ["jest-serializer-html"]
}

Vanilla JS Example

test('should beautify HTML', () => {
  expect('<ul><li><a href="#">My HTML</a></li></ul>').toMatchSnapshot();
});

Will output:

exports[`should beautify HTML 1`] = `
<ul>
  <li>
    <a href="#">
      My HTML
    </a>
  </li>
</ul>
`;

Vue.js component output example

import Vue from 'vue';
const Hello = {
  props: {
    msg: {
      type: String,
      default: 'World'
    }
  },
  template: `
    <h1>Hello ${ msg }!</h1>
    <ul id="main-list" class="list"><li><a href="#">My HTML</a></li></ul>
  `
};

test('should beautify HTML', () => {
  const Component = Vue.extend(Hello);
  const vm = new Component({
    propsData: {
      msg: 'You'
    }
  });

  vm.$mount();

  expect(vm.$el.outerHTML).toMatchSnapshot();
});

Will output:

exports[`should beautify HTML 1`] = `
<h1>
  Hello You!
</h1>
<ul id="main-list"
    class="list"
>
  <li>
    <a href="#">
      My HTML
    </a>
  </li>
</ul>
`;

You can read more about the HTML formatting here.

Special thanks

This package was inspired by the amazing post here: Jest for all: Episode 1 — Vue.js by Cristian Carlesso.