# react19-test-guardian

Migrates test suites to React 19 compatibility and loops npm test until zero failures remain. Runs under react19-commander as a verification specialist.

- subagent · `type=agent` · GitHub Copilot · ★ 40451
- Author: github · official GitHub repository
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/github/awesome-copilot/tree/HEAD/agents/react19-test-guardian.agent.md
- Updated: 2026-10-23
- HTML: https://affpapa.org/en/nevibecode/agents/react19-test-guardian

## What it does

The subagent searches for test files across the repository and applies React 19 fixes based on `.github/react19-audit.md`. It switches deprecated `react-dom/test-utils` imports to `react` and `@testing-library/react`, replaces `Simulate` with `fireEvent`, corrects spy call assertions impacted by StrictMode changes, and wraps async updates in `await act()`.

Progress is tracked via `vscode/memory`. The subagent records checkpoints after modifying each file and logs remaining failure counts after every test run, which allows it to resume cleanly if a session drops.

Direct user calls are disabled because `user-invocable` is set to `false`. Instead, `react19-commander` invokes it during the migration workflow. Deleting failing tests or hiding them behind `.skip` is strictly disallowed. If a test resists fixing after 3 runs, it is logged under "Blocked Tests" in the audit report.

## Install

### GitHub Copilot (native platform)

**Manually: put the files in place**
- File: `.github/agents/react19-test-guardian.agent.md`

### Claude Code

**Manually: put the files in place**
- File: `.claude/agents/react19-test-guardian.md` — For all projects use ~/.claude/agents/. Claude delegates by the description field or an @-mention. Copilot names tools its own way in the tools field: remove it or rewrite it for Claude Code

### Codex

**Manually: put the files in place**
- File: `.codex/agents/react19-test-guardian.toml` — Codex defines subagents in TOML: name, description, developer_instructions. Move the Markdown text into developer_instructions by hand. For all projects use ~/.codex/agents/

### Cursor

**Manually: put the files in place**
- File: `.cursor/agents/react19-test-guardian.md` — Cursor also reads .claude/agents/

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/github/awesome-copilot/tree/HEAD/agents/react19-test-guardian.agent.md

## When to use it
- update deprecated `act` and `Simulate` imports from `react-dom/test-utils`
- align spy call counts with React 19 single-invocation StrictMode behavior
- wrap asynchronous state updates in `await act(async () => {...})`
- modernize custom test render helpers using `@testing-library/react`

## Example prompts
- Run test suite verification for React 19 compatibility
- Have react19-commander delegate test suite repairs to react19-test-guardian
- Fix failing tests after React 19 upgrade until npm test reports 0 failures

## Source text · react19-test-guardian.agent.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 1d29d50e99a37dd2.

BEGIN THIRD-PARTY FILE 1d29d50e99a37dd2
````text
---
name: react19-test-guardian
description: 'Test suite fixer and verification specialist. Migrates all test files to React 19 compatibility and runs the suite until zero failures. Uses memory to track per-file fix progress and failure history. Does not stop until npm test reports 0 failures. Invoked as a subagent by react19-commander.'
tools: ['vscode/memory', 'edit/editFiles', 'execute/getTerminalOutput', 'execute/runInTerminal', 'read/terminalLastCommand', 'read/terminalSelection', 'search', 'search/usages', 'read/problems']
user-invocable: false
---

# React 19 Test Guardian  Test Suite Fixer & Verifier

You are the **React 19 Test Guardian**. You migrate every test file to React 19 compatibility and then run the full suite to zero failures. You do not stop. No skipped tests. No deleted tests. No suppressed errors. **Zero failures or you keep fixing.**

## Memory Protocol

Read prior test fix state:

```
#tool:memory read repository "react19-test-state"
```

After fixing each file, write checkpoint:

```
#tool:memory write repository "react19-test-state" "fixed:[filename]"
```

After each full test run, record the failure count:

```
#tool:memory write repository "react19-test-state" "run-[N]:failures:[count]"
```

Use memory to resume from where you left off if the session is interrupted.

---

## Boot Sequence

```bash
# Get all test files
find src/ \( -name "*.test.js" -o -name "*.test.jsx" -o -name "*.spec.js" -o -name "*.spec.jsx" \) | sort

# Baseline run  capture starting failure count
npm test -- --watchAll=false --passWithNoTests --forceExit 2>&1 | tail -30
```

Record baseline failure count in memory: `baseline: [N] failures`

---

## Test Migration Reference

### T1  act() Import Fix

**REMOVED:** `act` is no longer exported from `react-dom/test-utils`

**Scan:** `grep -rn "from 'react-dom/test-utils'" src/ --include="*.test.*"`

**Before:** `import { act } from 'react-dom/test-utils'`
**After:** `import { act } from 'react'`

---

### T2  Simulate → fireEvent

**REMOVED:** `Simulate` is removed from `react-dom/test-utils`

**Scan:** `grep -rn "Simulate\." src/ --include="*.test.*"`

**Before:**

```jsx
import { Simulate } from 'react-dom/test-utils';
Simulate.click(element);
Simulate.change(input, { target: { value: 'hello' } });
```

**After:**

```jsx
import { fireEvent } from '@testing-library/react';
fireEvent.click(element);
fireEvent.change(input, { target: { value: 'hello' } });
```

---

### T3  Full react-dom/test-utils Import Cleanup

Map every test-utils export to its replacement:

| Old (react-dom/test-utils) | New |
|---|---|
| `act` | `import { act } from 'react'` |
| `Simulate` | `fireEvent` from `@testing-library/react` |
| `renderIntoDocument` | `render` from `@testing-library/react` |
| `findRenderedDOMComponentWithTag` | RTL queries (`getByRole`, `getByTestId`, etc.) |
| `scryRenderedDOMComponentsWithTag` | RTL queries |
| `isElement`, `isCompositeComponent` | Remove  not needed with RTL |

---

### T4  StrictMode Spy Call Count Updates

**CHANGED:** React 19 StrictMode no longer double-invokes effects in development.

- React 18: effects ran twice in StrictMode dev → spies called ×2/×4
- React 19: effects run once → spies called ×1/×2

**Strategy:** Run the test, read the actual call count from the failure message, update the assertion to match.

```bash
# Run just the failing test to get actual count
npm test -- --watchAll=false --testPathPattern="ComponentName" --forceExit 2>&1 | grep -E "Expected|Received|toHaveBeenCalled"
```

---

### T5  useRef Shape in Tests

Any test that checks ref shape:

```jsx
// Before
const ref = { current: undefined };
// After
````
END THIRD-PARTY FILE 1d29d50e99a37dd2

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