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Disallow wrapping Testing Library utils or empty callbacks in act (testing-library/no-unnecessary-act)

⚠️ The act method is only available on the following Testing Library packages:

  • @testing-library/react (supported by this plugin)
  • @testing-library/preact (not supported yet by this plugin)
  • @testing-library/svelte (not supported yet by this plugin)

Rule Details

This rule aims to avoid the usage of act to wrap Testing Library utils just to silence "not wrapped in act(...)" warnings.

All Testing Library utils are already wrapped in act. Most of the time, if you're seeing an act warning, it's not just something to be silenced, but it's actually telling you that something unexpected is happening in your test.

Additionally, wrapping empty callbacks in act is also an incorrect way of silencing "not wrapped in act(...)" warnings.

Code violations reported by this rule will pinpoint those unnecessary act, helping to understand when act actually is necessary.

Example of incorrect code for this rule:

// ❌ wrapping things related to Testing Library in `act` is incorrect
import {
  act,
  render,
  screen,
  waitFor,
  fireEvent,
} from '@testing-library/react';
// ^ act imported from 'react-dom/test-utils' will be reported too
import userEvent from '@testing-library/user-event';

// ...

act(() => {
  render(<Example />);
});

await act(async () => waitFor(() => {}));

act(() => screen.getByRole('button'));

act(() => {
  fireEvent.click(element);
});

act(() => {
  userEvent.click(element);
});
// ❌ wrapping empty callbacks in `act` is incorrect
import { act } from '@testing-library/react';
// ^ act imported from 'react-dom/test-utils' will be reported too
import userEvent from '@testing-library/user-event';

// ...

act(() => {});

await act(async () => {});

Examples of correct code for this rule:

// ✅ wrapping things not related to Testing Library in `act` is correct
import { act } from '@testing-library/react';
import { stuffThatDoesNotUseRTL } from 'somwhere-else';

// ...

act(() => {
  stuffThatDoesNotUseRTL();
});
// ✅ wrapping both things related and not related to Testing Library in `act` is correct
import { act, screen } from '@testing-library/react';
import { stuffThatDoesNotUseRTL } from 'somwhere-else';

await act(async () => {
  await screen.findByRole('button');
  stuffThatDoesNotUseRTL();
});

Options

This rule has one option:

  • isStrict: disabled by default. Wrapping both things related and not related to Testing Library in act is reported

    "testing-library/no-unnecessary-act": ["error", {"isStrict": true}]

Incorrect:

// ❌ wrapping both things related and not related to Testing Library in `act` is NOT correct

import { act, screen } from '@testing-library/react';
import { stuffThatDoesNotUseRTL } from 'somwhere-else';

await act(async () => {
  await screen.findByRole('button');
  stuffThatDoesNotUseRTL();
});

Further Reading