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Testing React components

Translations: Espa帽ol, Fran莽ais

Setting up Babel

When you enable Babel, AVA 3 will automatically extend your regular (project-level) Babel configuration. You should be able to use React in your test files without any additional configuration.

However if you want to set it up explicitly, add the preset to the test options in AVA's Babel pipeline by modifying your package.json or ava.config.* file.

package.json:

{
	"ava": {
		"babel": {
			"testOptions": {
				"presets": ["@babel/preset-react"]
			}
		}
	}
}

You can find more information in @ava/babel.

Using Enzyme

Let's first see how to use AVA with one of the most popular React testing libraries: Enzyme.

If you intend to only use shallow component rendering, you don't need any extra setup.

Install Enzyme

First install Enzyme and its required adapter:

$ npm install --save-dev enzyme enzyme-adapter-react-16

Set up Enzyme

Create a helper file, prefixed with an underscore. This ensures AVA does not treat it as a test.

test/_setup-enzyme-adapter.js:

const Enzyme = require('enzyme');
const Adapter = require('enzyme-adapter-react-16');

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

Configure tests to use Enzyme

Configure AVA to require the helper before every test file.

package.json:

{
	"ava": {
		"require": [
			"./test/_setup-enzyme-adapter.js"
		]
	}
}

Enjoy

Then you can use Enzyme straight away:

test.js:

const test = require('ava');
const React = require('react');
const PropTypes = require('prop-types');
const {shallow} = require('enzyme');

const Foo = ({children}) =>
	<div className="Foo">
		<span className="bar">bar</span>
		{children}
		<span className="bar">bar</span>
	</div>;

Foo.propTypes = {
	children: PropTypes.any
};

test('has a .Foo class name', t => {
	const wrapper = shallow(<Foo/>);
	t.true(wrapper.hasClass('Foo'));
});

test('renders two `.Bar`', t => {
	const wrapper = shallow(<Foo/>);
	t.is(wrapper.find('.bar').length, 2);
});

test('renders children when passed in', t => {
	const wrapper = shallow(
		<Foo>
			<div className="unique"/>
		</Foo>
	);
	t.true(wrapper.contains(<div className="unique"/>));
});

Enzyme also has a mount and render helper to test in an actual browser environment. If you want to use these helpers, you will have to setup a browser environment. Check out the browser testing recipe on how to do so.

To see an example of AVA working together with Enzyme set up for browser testing, have a look at this sample project.

This is a basic example on how to integrate Enzyme with AVA. For more information about using Enzyme for unit testing React component, have a look at Enzyme's documentation.

Using JSX helpers

Another approach to testing React component is to use the react-element-to-jsx-string package to compare DOM trees as strings. jsx-test-helpers is a nice library handling shallow component rendering and converting JSX to string in order to test React components using AVA assertions.

$ npm install --save-dev jsx-test-helpers

Usage example:

const test = require('ava');
const React = require('react');
const PropTypes = require('prop-types');
const {renderJSX, JSX} = require('jsx-test-helpers');

const Foo = ({children}) =>
	<div className="Foo">
		<span className="bar">bar</span>
		{children}
		<span className="bar">bar</span>
	</div>;

Foo.propTypes = {
	children: PropTypes.any
};

test('renders correct markup', t => {
	const actual = renderJSX(<Foo/>);
	const expected = JSX(
		<div className="Foo">
			<span className="bar">bar</span>
			<span className="bar">bar</span>
		</div>
	);
	t.is(actual, expected);
});

test('renders children when passed in', t => {
	const actual = renderJSX(
		<Foo>
			<div className="unique"/>
		</Foo>
	);
	const expected = JSX(
		<div className="Foo">
			<span className="bar">bar</span>
			<div className="unique"/>
			<span className="bar">bar</span>
		</div>
	);
	t.is(actual, expected);
});

Note that you have to use variables like actual and expected because power-assert doesn't handle JSX correctly.

This is a basic example on how to use jsx-test-helpers with AVA. To see a more advanced usage of this library, have a look at this annotated test file.

This sample project shows a basic and minimal setup of AVA with jsx-test-helpers.

Using other assertion libraries

In AVA, you can use any assertion library, and there are already a few out there to test React components. Here is a list of assertion libraries working well with AVA: