@testing-library/react-native

What is @testing-library/react-native?

@testing-library/react-native is a testing library for React Native applications. It provides utilities to test React Native components in a way that resembles how users interact with your app. The library encourages writing tests that are more maintainable and less coupled to the implementation details of the components.

What are @testing-library/react-native's main functionalities?

Rendering Components

This feature allows you to render React Native components and query them for assertions. The example demonstrates rendering a simple Text component and verifying its content.

const { render } = require('@testing-library/react-native');
const { Text } = require('react-native');

const { getByText } = render(<Text>Hello, World!</Text>);
expect(getByText('Hello, World!')).toBeTruthy();

Fire Events

This feature allows you to simulate user interactions such as pressing a button. The example shows how to render a Button component and simulate a press event.

const { render, fireEvent } = require('@testing-library/react-native');
const { Button } = require('react-native');

const handlePress = jest.fn();
const { getByText } = render(<Button title="Press me" onPress={handlePress} />);
fireEvent.press(getByText('Press me'));
expect(handlePress).toHaveBeenCalled();

Async Utilities

This feature provides utilities to handle asynchronous operations in your components. The example demonstrates how to wait for a state change in a component that updates after a timeout.

const { render, waitFor } = require('@testing-library/react-native');
const { useEffect, useState } = require('react');
const { Text } = require('react-native');

const AsyncComponent = () => {
  const [data, setData] = useState(null);
  useEffect(() => {
    setTimeout(() => {
      setData('Loaded');
    }, 1000);
  }, []);
  return <Text>{data}</Text>;
};

const { getByText } = render(<AsyncComponent />);
await waitFor(() => expect(getByText('Loaded')).toBeTruthy());

Other packages similar to @testing-library/react-native

enzyme

Enzyme is a JavaScript testing utility for React that makes it easier to test your React Components' output. It provides a more detailed API for interacting with components, but it is more tightly coupled to the implementation details compared to @testing-library/react-native.

react-test-renderer

React Test Renderer is a package from the React team that allows you to render React components to pure JavaScript objects without depending on the DOM or a native mobile environment. It is useful for snapshot testing but does not provide the user-centric querying and event simulation features of @testing-library/react-native.

jest

Jest is a delightful JavaScript Testing Framework with a focus on simplicity. While Jest itself is not specific to React Native, it is often used in conjunction with @testing-library/react-native for assertions and mocking. Jest provides a comprehensive testing solution but lacks the specific utilities for interacting with React Native components that @testing-library/react-native offers.

README

React Native Testing Library

Simple and complete React Native testing utilities that encourage good testing practices.

The problem

You want to write maintainable tests for your React Native components. As a part of this goal, you want your tests to avoid including implementation details of your components and rather focus on making your tests give you the confidence for which they are intended. As part of this, you want your testbase to be maintainable in the long run so refactors of your components (changes to implementation but not functionality) don't break your tests and slow you and your team down.

This solution

The React Native Testing Library (RNTL) is a lightweight solution for testing React Native components. It provides light utility functions on top of react-test-renderer, in a way that encourages better testing practices. Its primary guiding principle is:

The more your tests resemble the way your software is used, the more confidence they can give you.

This project is inspired by React Testing Library. Tested to work with Jest, but it should work with other test runners as well.

Installation

Open a Terminal in your project's folder and run:

Using yarn

yarn add --dev @testing-library/react-native

Using npm

npm install --save-dev @testing-library/react-native

This library has a peerDependencies listing for react-test-renderer. Make sure that your react-test-renderer version matches exactly the react version.

Additional Jest matchers

In order to use additional React Native-specific jest matchers from @testing-library/jest-native package add it to your project:

Using yarn

yarn add --dev @testing-library/jest-native

Using npm

npm install --save-dev @testing-library/jest-native

Then automatically add it to your jest tests by using setupFilesAfterEnv option in your Jest configuration (it's usually located either in package.json under "jest" key or in a jest.config.json file):

{
  "preset": "react-native",
  "setupFilesAfterEnv": ["@testing-library/jest-native/extend-expect"]
}

Custom Jest Preset (React Native before 0.71)

We generally advise to use the "react-native" preset when testing with this library.

However, if you use React Native version earlier than 0.71 with modern Jest fake timers (default since Jest 27), you'll need to apply this custom Jest preset or otherwise awaiting promises, like using waitFor or findBy*, queries will fail with timeout.

This is a known issue. It happens because React Native's Jest preset overrides native Promise. Our preset restores it to defaults, which is not a problem in most apps out there.

Here's how you apply a custom preset in your Jest config:

{
  "preset": "@testing-library/react-native"
}

If this doesn't work for you, please fall back to using "legacy" fake timers.

Flow

Note for Flow users – you'll also need to install typings for react-test-renderer:

flow-typed install react-test-renderer

Example

import { render, screen, fireEvent } from '@testing-library/react-native';
import { QuestionsBoard } from '../QuestionsBoard';

test('form submits two answers', () => {
  const allQuestions = ['q1', 'q2'];
  const mockFn = jest.fn();

  render(<QuestionsBoard questions={allQuestions} onSubmit={mockFn} />);

  const answerInputs = screen.getAllByLabelText('answer input');

  fireEvent.changeText(answerInputs[0], 'a1');
  fireEvent.changeText(answerInputs[1], 'a2');
  fireEvent.press(screen.getByText('Submit'));

  expect(mockFn).toBeCalledWith({
    1: { q: 'q1', a: 'a1' },
    2: { q: 'q2', a: 'a2' },
  });
});

You can find the source of QuestionsBoard component and this example here.

API / Usage

The public API of @testing-library/react-native is focused around these essential methods:

• render – deeply renders given React element and returns helpers to query the output components.
• fireEvent - invokes named event handler on the element.
• waitFor - waits for non-deterministic periods of time until queried element is added or times out.
• waitForElementToBeRemoved - waits for non-deterministic periods of time until queried element is removed or times out.
• within - creates a queries object scoped for given element.

Migration Guides

• Migration to 12.0
• Migration to 11.0
• Migration to 9.0
• Migration to 7.0
• Migration to 2.0

Troubleshooting

• Troubleshooting guide

Related External Resources

• Real world extensive examples repo
• Where and how to start testing 🧪 your react-native app ⚛️ and how to keep on testin’
• Intro to React Native Testing Library & Jest Native

Made with ❤️ at Callstack

React Native Testing Library is an open source project and will always remain free to use. If you think it's cool, please star it 🌟. Callstack is a group of React and React Native geeks, contact us at [e-mail] if you need any help with these or just want to say hi!

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