React act() warning persists with latest versions (React 18.3.1 + RTL 16.3.0 + Vitest 2.1.0)

[nsxdavid]

Summary

The "Warning: The current testing environment is not configured to support act(...)" warning persists with the latest versions of React, React Testing Library, and Vitest as of January 2025.

Environment

• React: 18.3.1
• React DOM: 18.3.1
• @testing-library/react: 16.3.0
• Vitest: 2.1.0
• Node: 20+
• Environment: jsdom

Related Issues

This appears to be a continuation of:

• Warning: The current testing environment is not configured to support act(...) #1336 (June 2024) - Same warning with RTL v16
• RTL + Vitest issue with patching asyncWrapper/eventWrapper (with act()) for userEvent APIs #1338 (June 2024) - Vitest + RTL + userEvent warnings
• The current testing environment is not configured to support act(...) with vitest and React 18 #1061 (2022) - Original issue, claimed resolved but persists

Problem Description

Despite following all documented solutions and having the latest versions:

• ✅ React 18.3.1+ (required version)
• ✅ Single React version in dependency tree (verified with npm ls react)
• ✅ Latest @testing-library/react (16.3.0)
• ✅ Properly using act() from @testing-library/react
• ✅ Removed manual IS_REACT_ACT_ENVIRONMENT settings (as docs suggest these are ineffective in React 18.3.1+)

The warning still appears when running tests with Vitest.

Minimal Reproduction

import { render, screen, fireEvent, waitFor, act } from '@testing-library/react';
import { describe, it, expect, vi } from 'vitest';

const TestComponent = () => {
  const [loading, setLoading] = useState(false);
  
  const handleClick = async () => {
    setLoading(true);
    await fetch('/api/test');
    setLoading(false);
  };
  
  return (
    <button onClick={handleClick}>
      {loading ? 'Loading...' : 'Click me'}
    </button>
  );
};

describe('TestComponent', () => {
  it('should handle async state updates', async () => {
    global.fetch = vi.fn().mockResolvedValue({ ok: true });
    
    render(<TestComponent />);
    
    const button = screen.getByText('Click me');
    
    await act(async () => {
      fireEvent.click(button);
      await waitFor(() => {
        expect(screen.getByText('Loading...')).toBeInTheDocument();
      });
    });
    
    // Warning appears here despite proper act() usage
  });
});

Expected Behavior

No warnings when using act() properly with supported versions.

Actual Behavior

Warning: The current testing environment is not configured to support act(...)

Question for Maintainers

1. Is this a known limitation of the Vitest + React 18.3.1+ combination?
2. Is there a timeline for resolving this compatibility issue?
3. Should these warnings be considered acceptable/ignorable with the current tech stack?

Tests function correctly despite the warnings, but they create noise in CI/CD pipelines and developer workflows.

Additional Context

Multiple developers have reported this same issue across different projects with identical tech stacks, suggesting this is a systematic compatibility problem rather than individual configuration issues.

[llund]

I see his with the following stack:

• React 18.3.1
• RTL 16.3.0
• react-scripts 5.0.1

So it doesn't seem specific to vitest.

[bartektelec]

same problem

react@19.1.0
rtl@16.3.0
vitest@3.2.4