enzyme

What is enzyme?

Enzyme is a JavaScript testing utility for React that makes it easier to assert, manipulate, and traverse your React Components' output. It is designed to work with test runners like Jest or Mocha, and it provides a more intuitive and flexible API for interacting with React component trees.

What are enzyme's main functionalities?

Shallow Rendering

Shallow rendering is useful to constrain yourself to testing a component as a unit, and to ensure that your tests aren't indirectly asserting on behavior of child components.

import { shallow } from 'enzyme';
import MyComponent from './MyComponent';

const wrapper = shallow(<MyComponent />);
expect(wrapper.find('.my-class').length).toBe(1);

Full DOM Rendering

Full DOM rendering is ideal for use cases where you have components that may interact with DOM APIs, or may require the full lifecycle in order to fully test the component (i.e., componentDidMount etc.).

import { mount } from 'enzyme';
import MyComponent from './MyComponent';

const wrapper = mount(<MyComponent />);
expect(wrapper.find('.my-class').length).toBe(1);

Static Rendering

Static rendering is used to render the component to static HTML. It's useful for rendering components to strings, for instance, to send in emails, or for analyzing the markup structure.

import { render } from 'enzyme';
import MyComponent from './MyComponent';

const wrapper = render(<MyComponent />);
expect(wrapper.find('.my-class').length).toBe(1);

Other packages similar to enzyme

react-testing-library

React Testing Library is a very popular alternative to Enzyme that provides light utility functions on top of react-dom and react-dom/test-utils, in a way that encourages better testing practices. It focuses on testing components 'as the user would' rather than testing implementation details.

jest

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. It works well with React and can be used as a test runner, assertion library, and mocking library. Jest's snapshot testing feature can be seen as an alternative to Enzyme's rendering capabilities.

README

Enzyme

Enzyme is a JavaScript Testing utility for React that makes it easier to assert, manipulate, and traverse your React Components' output.

Enzyme's API is meant to be intuitive and flexible by mimicking jQuery's API for DOM manipulation and traversal.

Upgrading from Enzyme 2.x or React < 16

Are you here to check whether or not Enzyme is compatible with React 16? Are you currently using Enzyme 2.x? Great! Check out our migration guide for help moving on to Enzyme v3 where React 16 is supported.

Installation

To get started with enzyme, you can simply install it via npm. You will need to install enzyme along with an Adapter corresponding to the version of react (or other UI Component library) you are using. For instance, if you are using enzyme with React 16, you can run:

npm i --save-dev enzyme enzyme-adapter-react-16

Each adapter may have additional peer dependencies which you will need to install as well. For instance, enzyme-adapter-react-16 has peer dependencies on react and react-dom.

At the moment, Enzyme has adapters that provide compatibility with React 16.x, React 15.x, React 0.14.x and React 0.13.x.

The following adapters are officially provided by enzyme, and have the following compatibility with React:

Enzyme Adapter Package	React semver compatibility
enzyme-adapter-react-16	^16.4.0-0
enzyme-adapter-react-16.3	~16.3.0-0
enzyme-adapter-react-16.2	~16.2
enzyme-adapter-react-16.1	~16.0.0-0 || ~16.1
enzyme-adapter-react-15	^15.5.0
enzyme-adapter-react-15.4	15.0.0-0 - 15.4.x
enzyme-adapter-react-14	^0.14.0
enzyme-adapter-react-13	^0.13.0

Finally, you need to configure enzyme to use the adapter you want it to use. To do this, you can use the top level configure(...) API.

import Enzyme from 'enzyme';
import Adapter from 'enzyme-adapter-react-16';

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

3rd Party Adapters

It is possible for the community to create additional (non-official) adapters that will make enzyme work with other libraries. If you have made one and it's not included in the list below, feel free to make a PR to this README and add a link to it! The known 3rd party adapters are:

Adapter Package	For Library	Status
preact-enzyme-adapter	preact	(work in progress)
enzyme-adapter-inferno	inferno	(work in progress)

Running Enzyme Tests

Enzyme is unopinionated regarding which test runner or assertion library you use, and should be compatible with all major test runners and assertion libraries out there. The documentation and examples for enzyme use mocha and chai, but you should be able to extrapolate to your framework of choice.

If you are interested in using enzyme with custom assertions and convenience functions for testing your React components, you can consider using:

• chai-enzyme with Mocha/Chai.
• jasmine-enzyme with Jasmine.
• jest-enzyme with Jest.
• should-enzyme for should.js.
• expect-enzyme for expect.

Using Enzyme with Mocha

Using Enzyme with Karma

Using Enzyme with Browserify

Using Enzyme with SystemJS

Using Enzyme with Webpack

Using Enzyme with JSDOM

Using Enzyme with React Native

Using Enzyme with Jest

Using Enzyme with Lab

Using Enzyme with Tape and AVA

Basic Usage

Shallow Rendering

import React from 'react';
import { expect } from 'chai';
import { shallow } from 'enzyme';
import sinon from 'sinon';

import MyComponent from './MyComponent';
import Foo from './Foo';

describe('<MyComponent />', () => {
  it('renders three <Foo /> components', () => {
    const wrapper = shallow(<MyComponent />);
    expect(wrapper.find(Foo)).to.have.length(3);
  });

  it('renders an `.icon-star`', () => {
    const wrapper = shallow(<MyComponent />);
    expect(wrapper.find('.icon-star')).to.have.length(1);
  });

  it('renders children when passed in', () => {
    const wrapper = shallow((
      <MyComponent>
        <div className="unique" />
      </MyComponent>
    ));
    expect(wrapper.contains(<div className="unique" />)).to.equal(true);
  });

  it('simulates click events', () => {
    const onButtonClick = sinon.spy();
    const wrapper = shallow(<Foo onButtonClick={onButtonClick} />);
    wrapper.find('button').simulate('click');
    expect(onButtonClick).to.have.property('callCount', 1);
  });
});

Read the full API Documentation

Full DOM Rendering

import React from 'react';
import sinon from 'sinon';
import { expect } from 'chai';
import { mount } from 'enzyme';

import Foo from './Foo';

describe('<Foo />', () => {
  it('allows us to set props', () => {
    const wrapper = mount(<Foo bar="baz" />);
    expect(wrapper.props().bar).to.equal('baz');
    wrapper.setProps({ bar: 'foo' });
    expect(wrapper.props().bar).to.equal('foo');
  });

  it('simulates click events', () => {
    const onButtonClick = sinon.spy();
    const wrapper = mount((
      <Foo onButtonClick={onButtonClick} />
    ));
    wrapper.find('button').simulate('click');
    expect(onButtonClick).to.have.property('callCount', 1);
  });

  it('calls componentDidMount', () => {
    sinon.spy(Foo.prototype, 'componentDidMount');
    const wrapper = mount(<Foo />);
    expect(Foo.prototype.componentDidMount).to.have.property('callCount', 1);
    Foo.prototype.componentDidMount.restore();
  });
});

Read the full API Documentation

Static Rendered Markup

import React from 'react';
import { expect } from 'chai';
import { render } from 'enzyme';

import Foo from './Foo';

describe('<Foo />', () => {
  it('renders three `.foo-bar`s', () => {
    const wrapper = render(<Foo />);
    expect(wrapper.find('.foo-bar')).to.have.lengthOf(3);
  });

  it('renders the title', () => {
    const wrapper = render(<Foo title="unique" />);
    expect(wrapper.text()).to.contain('unique');
  });
});

Read the full API Documentation

Future

Enzyme Future

Contributing

See the Contributors Guide

In the wild

Organizations and projects using enzyme can list themselves here.

License

MIT

Changelog

3.4.4

Fixes

• @koba04: shallow: fix unexpected call to componentDidMount (#1768)