jest-native

Custom jest matchers to test the state of React Native.

The problem
This solution
Compatibility
Installation
Usage
- Extending Jest matchers
- TypeScript support
Matchers
Inspiration
Other solutions
Contributors

The problem

You want to use jest to write tests that assert various things about the state of a React Native app. As part of that goal, you want to avoid all the repetitive patterns that arise in doing so like checking for a native element's props, its text content, its styles, and more.

This solution

The jest-native library provides a set of custom jest matchers that you can use to extend jest. These will make your tests more declarative, clear to read and to maintain.

Compatibility

These matchers should, for the most part, be agnostic enough to work with any React Native testing utilities, but they are primarily intended to be used with React Native Testing Library. Any issues raised with existing matchers or any newly proposed matchers must be viewed through compatibility with that library and its guiding principles first.

Installation

This module should be installed as one of your project's devDependencies:

Using `yarn`

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

Using `npm`

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

You will need react-test-renderer, react, and react-native installed in order to use this package.

Usage

Extending Jest matchers

Import @testing-library/jest-native/extend-expect once (for instance in your tests setup file) and you're good to go:

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

Alternatively, you can selectively import only the matchers you intend to use, and extend jest's expect yourself:

import { toBeEmptyElement, toHaveTextContent } from '@testing-library/jest-native';

expect.extend({ toBeEmptyElement, toHaveTextContent });

TypeScript support

In order to setup proper TypeScript type checking use either one of the following approches.

1. Use TypeScript Jest setup file.

Use jest-setup.ts file (instead of jest-setup.js file) which is added to Jest config's setupFilesAfterEnv option.

The Jest setup file should contain following line:

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

This should enable TypeScript checkign for both tsc and VS Code intellisense.

2. Use `declarations.d.ts` file

Alternatively, create declarations.d.ts file at the root level of your project, if it does not exist already.

Add following line at the top of your declarations.d.ts:

/// <reference types="@testing-library/jest-native" />

This should enable TypeScript checkign for both tsc and VS Code intellisense.

Matchers

jest-native has only been tested to work with React Native Testing Library. Keep in mind that these queries are intended only to work with elements corresponding to host components.

`toBeDisabled`

toBeDisabled();

Check whether or not an element is disabled from a user perspective.

This matcher will check if the element or its parent has any of the following props :

disabled
accessibilityState={{ disabled: true }}
editable={false} (for TextInput only)

Examples

const { getByTestId } = render(
  <View>
    <Button disabled testID="button" title="submit" onPress={(e) => e} />
    <TextInput accessibilityState={{ disabled: true }} testID="input" value="text" />
  </View>,
);

expect(getByTestId('button')).toBeDisabled();
expect(getByTestId('input')).toBeDisabled();

`toBeEnabled`

toBeEnabled();

Check whether or not an element is enabled from a user perspective.

Works similarly to expect().not.toBeDisabled().

Examples

const { getByTestId } = render(
  <View>
    <Button testID="button" title="submit" onPress={(e) => e} />
    <TextInput testID="input" value="text" />
  </View>,
);

expect(getByTestId('button')).toBeEnabled();
expect(getByTestId('input')).toBeEnabled();

`toBeEmptyElement`

toBeEmptyElement();

Check that the given element has no content.

Examples

const { getByTestId } = render(<View testID="empty" />);

expect(getByTestId('empty')).toBeEmptyElement();

Note
This matcher has been previously named toBeEmpty(), but we changed that name in order to avoid conflict with Jest Extendend matcher with the same name.

`toContainElement`

toContainElement(element: ReactTestInstance | null);

Check if an element contains another element as a descendant. Again, will only work for native elements.

Examples

const { queryByTestId } = render(
  <View testID="grandparent">
    <View testID="parent">
      <View testID="child" />
    </View>
    <Text testID="text-element" />
  </View>,
);

const grandparent = queryByTestId('grandparent');
const parent = queryByTestId('parent');
const child = queryByTestId('child');
const textElement = queryByTestId('text-element');

expect(grandparent).toContainElement(parent);
expect(grandparent).toContainElement(child);
expect(grandparent).toContainElement(textElement);
expect(parent).toContainElement(child);
expect(parent).not.toContainElement(grandparent);

`toBeOnTheScreen`

toBeOnTheScreen();

Check that the element is present in the element tree.

You can check that an already captured element has not been removed from the element tree.

Note
This matcher requires React Native Testing Library v10.1 or later, as it includes the screen object.

Note
If you're using React Native Testing Library v12 or later, you need to install Jest Native v5.4.2 or later.

Examples

render(
  <View>
    <View testID="child" />
  </View>,
);

const child = screen.getByTestId('child');
expect(child).toBeOnTheScreen();

screen.update(<View />);
expect(child).not.toBeOnTheScreen();

`toHaveProp`

toHaveProp(prop: string, value?: any);

Check that the element has a given prop.

You can optionally check that the attribute has a specific expected value.

Examples

const { queryByTestId } = render(
  <View>
    <Text allowFontScaling={false} testID="text">
      text
    </Text>
    <Button disabled testID="button" title="ok" />
  </View>,
);

expect(queryByTestId('button')).toHaveProp('accessible');
expect(queryByTestId('button')).not.toHaveProp('disabled');
expect(queryByTestId('button')).not.toHaveProp('title', 'ok');

`toHaveTextContent`

toHaveTextContent(text: string | RegExp, options?: { normalizeWhitespace: boolean });

Check if an element or its children have the supplied text.

This will perform a partial, case-sensitive match when a string match is provided. To perform a case-insensitive match, you can use a RegExp with the /i modifier.

To enforce matching the complete text content, pass a RegExp.

Examples

const { queryByTestId } = render(<Text testID="count-value">2</Text>);

expect(queryByTestId('count-value')).toHaveTextContent('2');
expect(queryByTestId('count-value')).toHaveTextContent(2);
expect(queryByTestId('count-value')).toHaveTextContent(/2/);
expect(queryByTestId('count-value')).not.toHaveTextContent('21');

`toHaveStyle`

toHaveStyle(style: object[] | object);

Check if an element has the supplied styles.

You can pass either an object of React Native style properties, or an array of objects with style properties. You cannot pass properties from a React Native stylesheet.

Examples

const styles = StyleSheet.create({ text: { fontSize: 16 } });

const { queryByText } = render(
  <Text
    style={[
      { color: 'black', fontWeight: '600', transform: [{ scale: 2 }, { rotate: '45deg' }] },
      styles.text,
    ]}
  >
    Hello World
  </Text>,
);

expect(getByText('Hello World')).toHaveStyle({ color: 'black' });
expect(getByText('Hello World')).toHaveStyle({ fontWeight: '600' });
expect(getByText('Hello World')).toHaveStyle({ fontSize: 16 });
expect(getByText('Hello World')).toHaveStyle([{ fontWeight: '600' }, { color: 'black' }]);
expect(getByText('Hello World')).toHaveStyle({ color: 'black', fontWeight: '600', fontSize: 16 });
expect(getByText('Hello World')).toHaveStyle({ transform: [{ scale: 2 }, { rotate: '45deg' }] });
expect(getByText('Hello World')).not.toHaveStyle({ color: 'white' });
expect(getByText('Hello World')).not.toHaveStyle({ transform: [{ scale: 2 }] });
expect(getByText('Hello World')).not.toHaveStyle({
  transform: [{ rotate: '45deg' }, { scale: 2 }],
});

`toBeVisible`

toBeVisible();

Check that the given element is visible to the user.

An element is visible if all the following conditions are met:

it does not have its style property display set to none.
it does not have its style property opacity set to 0.
it is not a Modal component or it does not have the prop visible set to false.
it is not hidden from accessibility as checked by isHiddenFromAccessibility function from React Native Testing Library
its ancestor elements are also visible.

Examples

const { getByTestId } = render(<View testID="empty-view" />);

expect(getByTestId('empty-view')).toBeVisible();

const { getByTestId } = render(<View testID="view-with-opacity" style={{ opacity: 0.2 }} />);

expect(getByTestId('view-with-opacity')).toBeVisible();

const { getByTestId } = render(<Modal testID="empty-modal" />);

expect(getByTestId('empty-modal')).toBeVisible();

const { getByTestId } = render(
  <Modal>
    <View>
      <View testID="view-within-modal" />
    </View>
  </Modal>,
);

expect(getByTestId('view-within-modal')).toBeVisible();

const { getByTestId } = render(<View testID="invisible-view" style={{ opacity: 0 }} />);

expect(getByTestId('invisible-view')).not.toBeVisible();

const { getByTestId } = render(<View testID="display-none-view" style={{ display: 'none' }} />);

expect(getByTestId('display-none-view')).not.toBeVisible();

const { getByTestId } = render(
  <View style={{ opacity: 0 }}>
    <View>
      <View testID="view-within-invisible-view" />
    </View>
  </View>,
);

expect(getByTestId('view-within-invisible-view')).not.toBeVisible();

const { getByTestId } = render(
  <View style={{ display: 'none' }}>
    <View>
      <View testID="view-within-display-none-view" />
    </View>
  </View>,
);

expect(getByTestId('view-within-display-none-view')).not.toBeVisible();

const { getByTestId } = render(
  <Modal visible={false}>
    <View>
      <View testID="view-within-not-visible-modal" />
    </View>
  </Modal>,
);

// Children elements of not visible modals are not rendered.
expect(queryByTestId('view-within-modal')).toBeNull();

const { getByTestId } = render(<Modal testID="not-visible-modal" visible={false} />);

expect(getByTestId('not-visible-modal')).not.toBeVisible();

const { getByTestId } = render(<View testID="test" accessibilityElementsHidden />);

expect(getByTestId('test')).not.toBeVisible();

const { getByTestId } = render(
  <View testID="test" importantForAccessibility="no-hide-descendants" />,
);

expect(getByTestId('test')).not.toBeVisible();

`toHaveAccessibilityState`

toHaveAccessibilityState(state: {
  disabled?: boolean;
  selected?: boolean;
  checked?: boolean | 'mixed';
  busy?: boolean;
  expanded?: boolean;
});

Check that the element has given accessibility state entries.

This check is based on accessibilityState prop but also takes into account the default entries which have been found by experimenting with accessibility inspector and screen readers on both iOS and Android.

Some state entries behave as if explicit false value is the same as not having given state entry, so their default value is false:

disabled
selected
busy

The remaining state entries behave as if explicit false value is different than not having given state entry, so their default value is undefined:

checked
expanded

This matcher is compatible with *ByRole and *ByA11State queries from React Native Testing Library.

Examples

render(<View testID="view" accessibilityState={{ expanded: true, checked: true }} />);

// Single value match
expect(screen.getByTestId('view')).toHaveAccessibilityState({ expanded: true });
expect(screen.getByTestId('view')).toHaveAccessibilityState({ checked: true });

// Can match multiple entries
expect(screen.getByTestId('view')).toHaveAccessibilityState({ expanded: true, checked: true });

Default values handling:

render(<View testID="view" />);

// Matching states where default value is `false`
expect(screen.getByTestId('view')).toHaveAccessibilityState({ disabled: false });
expect(screen.getByTestId('view')).toHaveAccessibilityState({ selected: false });
expect(screen.getByTestId('view')).toHaveAccessibilityState({ busy: false });

// Matching states where default value is `undefined`
expect(screen.getByTestId('view')).not.toHaveAccessibilityState({ checked: false });
expect(screen.getByTestId('view')).not.toHaveAccessibilityState({ expanded: false });

`toHaveAccessibilityValue`

toHaveAccessibilityValue(value: {
  min?: number;
  max?: number;
  now?: number;
  text?: string | RegExp;
});

Check that the element has given accessibilityValue prop entries.

This matcher is compatible with *ByRole and *ByA11Value queries from React Native Testing Library.

Examples

render(<View testID="view" accessibilityValue={{ min: 0, max: 100, now: 65 }} />);

const view = screen.getByTestId('view');

// Single value match
expect(view).toHaveAccessibilityValue({ now: 65 });
expect(view).toHaveAccessibilityValue({ max: 0 });

// Can match multiple entries
expect(view).toHaveAccessibilityValue({ min: 0, max: 100 });
expect(view).toHaveAccessibilityValue({ min: 0, max: 100, now: 65 });

// All specified entries need to match
expect(view).not.toHaveAccessibilityValue({ now: 45 });
expect(view).not.toHaveAccessibilityValue({ min: 20, max: 100, now: 65 });

render(<View testID="view" accessibilityValue={{ text: 'Almost full' }} />);

const view = screen.getByTestId('view');
expect(view).toHaveAccessibilityValue({ text: 'Almost full' });
expect(view).toHaveAccessibilityValue({ text: /full/ });

Inspiration

This library was made to be a companion for React Native Testing Library.

It was inspired by jest-dom, the companion library for DTL. We emulated as many of those helpers as we could while keeping in mind the guiding principles.