RITEway-Jest

Inspired by Eric Elliott's RITEway.

Why?

TLDR: I wanted RITEway's assert for Jest.

I love RITEway's API because it forces you to write good unit tests by it's given-should API and only exposing the equals assertion.

Only problem is RITEway is build using tape. You can't use it with Jest, which in turn has some advantages and disadvantages.

Disadvantages

• You can't use it to test React Native components because Jest has the only good, up to date React Native mock.
• There might be some other Jest features that RITEway lacks.
• I know this is minor, but you also have to do more setup compared to Jest, which just works™ for React Native and React apps created with CRA.

Advantages

• RITEway forces you to split your components' tests in an effective way. This means only testing display components and their respective split off pure logic with unit tests, while covering the rest of your code using E2E tests.
• You can't mock.

You might want to check out RITEway because you can learn these advantages first hand. I prefer RITEway for React apps and use RITEway-Jest for React Native apps.

Installation

npm i --save-dev riteway-jest

or

yarn add --dev riteway-jest

Setup

React with CRA

Add an import in your src/setupTests.js.

import 'riteway-jest/src/riteway-jest.js';

React Native

Add to your jest key in package.json.

"jest": {
  "preset": "react-native",
  "setupFilesAfterEnv": ["node_modules/riteway-jest/src/riteway-jest.js"]
}

React Native with Expo

Add to your jest key in package.json.

"jest": {
  "preset": "jest-expo",
  "setupFilesAfterEnv": ["node_modules/riteway-jest/src/riteway-jest.js"]
}

jest.config.js instead of package.json.

module.exports = {
  setupFilesAfterEnv: [
    'node_modules/riteway-jest/src/riteway-jest.js',
    // ... other setup files ...
  ],
  // ... other options ...
};

Tips

ESLint complains

Add a global key to your .eslintrc.json.

{
  "_comment": "<Your other settings here>",
  "globals": {
    "assert": 'readonly'
  },
  "rules": {
    "_comment": "<Your rules here>"
  }
}

Usage

With pure functions.

const sum = (a = 0, b = 0) => a + b;

describe('sum()', () => {
  const should = 'return the correct sum';

  assert({
    given: 'no arguments',
    should: 'return 0',
    actual: sum(),
    expected: 0,
  });

  assert({
    given: 'zero',
    should,
    actual: sum(2, 0),
    expected: 2,
  });

  assert({
    given: 'negative numbers',
    should,
    actual: sum(1, -4),
    expected: -3,
  });
});

Using React Native Testing Library.

import React from 'react';
import { Text } from 'react-native';
import { render } from 'react-native-testing-library';

function MyText({ title }) {
  return <Text>{title}</Text>;
}

describe('Text component', () => {
  const createText = (props = {}) => render(<MyText {...props} />);

  {
    const props = { title: 'Foo' };
    const $ = createText(props).getByType;

    assert({
      given: 'a title',
      should: 'display the title',
      actual: $('Text').props.children,
      expected: props.title,
    });
  }
});

Using React Testing Library.

import PropTypes from 'prop-types';
import React from 'react';
import { cleanup, render } from 'react-testing-library';

function Button({ disabled, onClick, text }) {
  return (
    <button data-testid="foo" disabled={disabled} onClick={onClick}>
      {text}
    </button>
  );
}

Button.propTypes = {
  disabled: PropTypes.bool.isRequired,
  onClick: PropTypes.func.isRequired,
  text: PropTypes.string,
};

Button.defaultProps = {
  disabled: false,
  text: '',
};

describe('button component', () => {
  const createButton = (props = {}) =>
    render(<Button onClick={() => {}} {...props} />);

  {
    const props = { text: 'foo' };
    const $ = createButton(props).getByTestId;

    assert({
      given: 'a text',
      should: "render 'foo'",
      actual: $('foo').textContent,
      expected: props.text,
    });
    cleanup();
  }

  {
    const props = { disabled: true, text: 'foo' };
    const $ = createButton(props).getByText;

    assert({
      given: 'disabled',
      should: 'be disabled',
      actual: $('foo').hasAttribute('disabled'),
      expected: props.disabled,
    });
    cleanup();
  }
});

skip & only & todo

assert supports Jest's skip, only and todo functions.

// This test is explicitly skipped
assert.skip({
  given: 'something',
  should: 'be equal to something',
  actual: 'nothing',
  expected: 'something',
});

// This test gets executed
assert.only({
  given: 'something',
  should: 'be equal to something',
  actual: 'nothing',
  expected: 'something',
});

// This test is implicitly skipped because the .only() above
assert({
  given: 'something',
  should: 'be equal to something',
  actual: 'nothing',
  expected: 'something',
});

each is currently not supported.