@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

Developer-friendly 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 tests 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 comprehensive solution for testing React Native components. It provides React Native runtime simulation 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:

# Yarn install:
yarn add --dev @testing-library/react-native

# NPM install
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, avoid using ^ in version number.

Additional Jest matchers

You can use the built-in Jest matchers by adding the following line to your jest-setup.ts file (configured using setupFilesAfterEnv):

import '@testing-library/react-native/extend-expect';

Example

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

// It is recommended to use userEvent with fake timers
// Some events involve duration so your tests may take a long time to run.
jest.useFakeTimers();

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

  const user = userEvent.setup();
  render(<QuestionsBoard questions={questions} onSubmit={onSubmit} />);

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

  // simulates the user focusing on TextInput and typing text one char at a time
  await user.type(answerInputs[0], 'a1');
  await user.type(answerInputs[1], 'a2');

  // simulates the user pressing on any pressable element
  await user.press(screen.getByRole('button', { name: 'Submit' }));

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

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

API / Usage

React Native Testing Library consists of following APIs:

• render function - render your UI components for testing purposes
• screen object - access rendered UI:
  • Queries - find rendered components by various predicates: role, text, test ids, etc
  • Lifecycle methods: rerender, unmount
  • Helpers: debug, toJSON, root
• Jest matchers - validate assumptions about your UI
• User Event - simulate common user interactions like press or type in a realistic way
• Fire Event - simulate any component event in a simplified way
• renderHook function - render hooks for testing purposes
• Miscellaneous APIs:
  • Async utils: findBy* queries, waitFor, waitForElementToBeRemoved
  • Configuration: configure, resetToDefaults
  • Accessibility: isHiddenFromAccessibility
  • Other: within, act, cleanup

Migration Guides

• Migration to 12.0
• Migration to built-in Jest Matchers

Troubleshooting

• Troubleshooting guide

Community Resources

Check out our list of Community Resources about RNTL.

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!

Like the project? ⚛️ Join the team who does amazing stuff for clients and drives React Native Open Source! 🔥

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