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Getting Started

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 focus on making your tests give you the confidence 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 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 how your software is used, the more confidence they can give you.

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

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

Installation​

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

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

This library has a peer dependency for react-test-renderer package. Make sure that your react-test-renderer version matches exactly your react version.

Jest matchers​

To set up React Native-specific Jest matchers, add the following line to your jest-setup.ts file (configured using setupFilesAfterEnv):

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

ESLint plugin​

We recommend setting up eslint-plugin-testing-library package to help you avoid common Testing Library mistakes and bad practices.

Install the plugin (assuming you already have eslint installed & configured):

npm install --save-dev eslint-plugin-testing-library

Then, add relevant entry to your ESLint config (e.g., .eslintrc.js). We recommend extending the react plugin:

module.exports = {
  overrides: [
    {
      // Test files only
      files: ['**/__tests__/**/*.[jt]s?(x)', '**/?(*.)+(spec|test).[jt]s?(x)'],
      extends: ['plugin:testing-library/react']
    }
  ]
};

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 the QuestionsBoard component and this example here.