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Other APIs

Async utilities​

findBy* queries​

The findBy* queries are used to find elements that are not instantly available but will be added as a result of some asynchronous action. Learn more details here.

waitFor​

function waitFor<T>(
  expectation: () => T,
  { timeout: number = 1000, interval: number = 50 },
): Promise<T> {}

Waits for a period of time for the expectation callback to pass. waitFor may run the callback a number of times until timeout is reached, as specified by the timeout and interval options. The callback must throw an error when the expectation is not met. Returning any value, including a falsy one, will be treated as meeting the expectation, and the callback result will be returned to the caller of waitFor function.

await waitFor(() => expect(mockFunction).toHaveBeenCalledWith());

waitFor function will be executing expectation callback every interval (default: every 50 ms) until timeout (default: 1000 ms) is reached. The repeated execution of callback is stopped as soon as it does not throw an error, in such case the value returned by the callback is returned to waitFor caller. Otherwise, when it reaches the timeout, the final error thrown by expectation will be re-thrown by waitFor to the calling code.

// ❌ `waitFor` will return immediately because callback does not throw
await waitFor(() => false);

waitFor is an async function so you need to await the result to pause test execution.

// ❌ missing `await`: `waitFor` will just return Promise that will be rejected when the timeout is reached
waitFor(() => expect(1).toBe(2));
note

You can enforce awaiting waitFor by using the await-async-utils rule from eslint-plugin-testing-library.

Since waitFor is likely to run expectation callback multiple times, it is highly recommended for it not to perform any side effects in waitFor.

await waitFor(() => {
  // ❌ button will be pressed on each waitFor iteration
  fireEvent.press(screen.getByText('press me'));
  expect(mockOnPress).toHaveBeenCalled();
});
note

Avoiding side effects in expectation callback can be partially enforced with the no-wait-for-side-effects rule.

It is also recommended to have a single assertion per each waitFor for more consistency and faster failing tests. If you want to make several assertions, then they should be in seperate waitFor calls. In many cases you won't actually need to wrap the second assertion in waitFor since the first one will do the waiting required for asynchronous change to happen.

Using a React Native version < 0.71 with Jest fake timers​

caution

When using a version of React Native < 0.71 and modern fake timers (the default for Jest >= 27), waitFor won't work (it will always timeout even if expectation() doesn't throw) unless you use the custom @testing-library/react-native preset.

waitFor checks whether Jest fake timers are enabled and adapts its behavior in such case. The following snippet is a simplified version of how it behaves when fake timers are enabled:

let fakeTimeRemaining = timeout;
let lastError;

while (fakeTimeRemaining > 0) {
  fakeTimeRemaining = fakeTimeRemaining - interval;
  jest.advanceTimersByTime(interval);
  try {
    // resolve
    return expectation();
  } catch (error) {
    lastError = error;
  }
}

// reject
throw lastError;

In the following example we test that a function is called after 10 seconds using fake timers. Since we're using fake timers, the test won't depend on real time passing and thus be much faster and more reliable. Also we don't have to advance fake timers through Jest fake timers API because waitFor already does this for us.

// in component
setTimeout(() => {
  someFunction();
}, 10000);

// in test
jest.useFakeTimers();

await waitFor(() => {
  expect(someFunction).toHaveBeenCalledWith();
}, 10000);
info

In order to properly use waitFor you need at least React >=16.9.0 (featuring async act) or React Native >=0.61 (which comes with React >=16.9.0).

note

If you receive warnings related to act() function consult our Undestanding Act function document.

waitForElementToBeRemoved​

function waitForElementToBeRemoved<T>(
  expectation: () => T,
  { timeout: number = 4500, interval: number = 50 },
): Promise<T> {}

Waits for non-deterministic periods of time until queried element is removed or times out. waitForElementToBeRemoved periodically calls expectation every interval milliseconds to determine whether the element has been removed or not.

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

test('waiting for an Banana to be removed', async () => {
  render(<Banana />);

  await waitForElementToBeRemoved(() => screen.getByText('Banana ready'));
});

This method expects that the element is initially present in the render tree and then is removed from it. If the element is not present when you call this method it throws an error.

You can use any of getBy, getAllBy, queryBy and queryAllBy queries for expectation parameter.

info

In order to properly use waitForElementToBeRemoved you need at least React >=16.9.0 (featuring async act) or React Native >=0.61 (which comes with React >=16.9.0).

note

If you receive warnings related to act() function consult our Undestanding Act function document.

Configuration​

configure​

type Config = {
  asyncUtilTimeout: number;
  defaultHidden: boolean;
  defaultDebugOptions: Partial<DebugOptions>;
};

function configure(options: Partial<Config>) {}

asyncUtilTimeout option​

Default timeout, in ms, for async helper functions (waitFor, waitForElementToBeRemoved) and findBy* queries. Defaults to 1000 ms.

defaultIncludeHiddenElements option​

Default value for includeHiddenElements query option for all queries. The default value is set to false, so all queries will not match elements hidden from accessibility. This is because the users of the app would not be able to see such elements.

This option is also available as defaultHidden alias for compatibility with React Testing Library.

defaultDebugOptions option​

Default debug options to be used when calling debug(). These default options will be overridden by the ones you specify directly when calling debug().

resetToDefaults()​

function resetToDefaults() {}

Environment variables​

RNTL_SKIP_AUTO_CLEANUP​

Set to true to disable automatic cleanup() after each test. It works the same as importing react-native-testing-library/dont-cleanup-after-each or using react-native-testing-library/pure.

$ RNTL_SKIP_AUTO_CLEANUP=true jest

RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS​

Set to true to disable auto-detection of fake timers. This might be useful in rare cases when you want to use non-Jest fake timers. See issue #886 for more details.

$ RNTL_SKIP_AUTO_DETECT_FAKE_TIMERS=true jest

Accessibility​

isHiddenFromAccessibility​

function isHiddenFromAccessibility(element: ReactTestInstance | null): boolean {}

Also available as isInaccessible() alias for React Testing Library compatibility.

Checks if given element is hidden from assistive technology, e.g. screen readers.

note

Like isInaccessible function from DOM Testing Library this function considers both accessibility elements and presentational elements (regular Views) to be accessible, unless they are hidden in terms of host platform.

This covers only part of ARIA notion of Accessiblity Tree, as ARIA excludes both hidden and presentational elements from the Accessibility Tree.

For the scope of this function, element is inaccessible when it, or any of its ancestors, meets any of the following conditions:

Specifying accessible={false}, accessiblityRole="none", or importantForAccessibility="no" props does not cause the element to become inaccessible.

Other helpers​

within, getQueriesForElement​

function within(element: ReactTestInstance): Queries {}

function getQueriesForElement(element: ReactTestInstance): Queries {}

within (also available as getQueriesForElement alias) performs queries scoped to given element.

note

Please note that additional render specific operations like update, unmount, debug, toJSON are not included.

const detailsScreen = within(screen.getByA11yHint('Details Screen'));
expect(detailsScreen.getByText('Some Text')).toBeOnTheScreen();
expect(detailsScreen.getByDisplayValue('Some Value')).toBeOnTheScreen();
expect(detailsScreen.queryByLabelText('Some Label')).toBeOnTheScreen();
await expect(detailsScreen.findByA11yHint('Some Label')).resolves.toBeOnTheScreen();

Use cases for scoped queries include:

  • queries scoped to a single item inside a FlatList containing many items
  • queries scoped to a single screen in tests involving screen transitions (e.g. with react-navigation)

act​

Useful function to help testing components that use hooks API. By default any render, update, fireEvent, and waitFor calls are wrapped by this function, so there is no need to wrap it manually. This method is re-exported from react-test-renderer.

Consult our Undestanding Act function document for more understanding of its intricacies.

cleanup​

const cleanup: () => void;

Unmounts React trees that were mounted with render and clears screen variable that holds latest render output.

info

Please note that this is done automatically if the testing framework you're using supports the afterEach global (like mocha, Jest, and Jasmine). If not, you will need to do manual cleanups after each test.

For example, if you're using the jest testing framework, then you would need to use the afterEach hook like so:

import { cleanup, render } from '@testing-library/react-native/pure';
import { View } from 'react-native';

afterEach(cleanup);

it('renders a view', () => {
  render(<View />);
  // ...
});

The afterEach(cleanup) call also works in describe blocks:

describe('when logged in', () => {
  afterEach(cleanup);

  it('renders the user', () => {
    render(<SiteHeader />);
    // ...
  });
});

Failing to call cleanup when you've called render could result in a memory leak and tests which are not "idempotent" (which can lead to difficult to debug errors in your tests).