Bug: React 18.3 warning says to import `act` from `react`, only `unstable_act` exists

[rexxars]

In the newly released 18.3.0 release, if you try to use the act function from react-dom/test-utils, you will get the following warning:

Import act from react instead of react-dom/test-utils

However, the 18.3.0 release only ships unstable_act, not act. The react 19 beta seems to have renamed to act.
I feel the warning should either tell you to import from unstable_act, or the act export should actually exist, even if aliased to unstable_act internally

React version: 18.3.0

Steps To Reproduce

1. On react + react-dom@18.3.0, import and use act from react-dom/test-utils.
2. See warning
3. Try to import act from react@18.3.0

Link to code example: https://codesandbox.io/p/sandbox/intelligent-chandrasekhar-p9xk7h

The current behavior

act does not exist, warning tells you to use it

The expected behavior

act exists, warning tells you to use it OR warning tells you to use unstable_act

[Codex-]

Also encountered this. Worth noting that the recommended @testing-library/react package will emit this too as a result of what's reported here.

They attempt to use what is requested by react, but fallback to the deprecated usage due to act being undefined on react itself

import * as React from 'react'
import * as DeprecatedReactTestUtils from 'react-dom/test-utils'

const reactAct = typeof React.act === 'function' ? React.act : DeprecatedReactTestUtils.act

source

[rickhanlonii]

Nice catch, will fix in #28916

[acdlite]

Fixed in 18.3.1, thanks for reporting!

[sairamg08]

@acdlite This issue not fixed in ract 18.3.1,

Created using pnpm create react-app

"dependencies": { "@testing-library/jest-dom": "^5.17.0", "@testing-library/react": "^13.4.0", "@testing-library/user-event": "^13.5.0", "react": "^18.3.1", "react-dom": "^18.3.1", "react-scripts": "5.0.1", "web-vitals": "^2.1.4" },

command:
pnpm run test

console.error
Warning: ReactDOMTestUtils.act is deprecated in favor of React.act. Import act from react instead of react-dom/test-utils. See https://react.dev/warnings/react-dom-test-utils for more info.

  3 |
  4 | test('renders learn react link', () => {
> 5 |   render(<App />);
    |         ^
  6 |   const linkElement = screen.getByText(/learn react/i);
  7 |   expect(linkElement).toBeInTheDocument();
  8 | });

  at printWarning (node_modules/react-dom/cjs/react-dom-test-utils.development.js:71:30)
  at error (node_modules/react-dom/cjs/react-dom-test-utils.development.js:45:7)
  at actWithWarning (node_modules/react-dom/cjs/react-dom-test-utils.development.js:1736:7)
  at node_modules/@testing-library/react/dist/act-compat.js:63:25
  at renderRoot (node_modules/@testing-library/react/dist/pure.js:159:26)
  at render (node_modules/@testing-library/react/dist/pure.js:246:10)
  at Object.<anonymous> (src/App.test.js:5:9)
  at TestScheduler.scheduleTests (node_modules/@jest/core/build/TestScheduler.js:333:13)
  at runJest (node_modules/@jest/core/build/runJest.js:404:19)

PASS src/App.test.js
✓ renders learn react link (40 ms)

Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 0.543 s, estimated 1 s
Ran all test suites.

Watch Usage: Press w to show more.

[rexxars]

@acdlite This issue not fixed in ract 18.3.1,

It is fixed. What you are seeing is a warning about the act method from react-dom/test-utils being deprecated. This issue is about the act method not being available on React 18.3.0 (through the react module). In React 18.3.1, act is available and should be used.