limrun-detox-testing — Claude Code skill: what it does, how to install

---
name: limrun-detox-testing
description: Configure, run, or debug Detox on Limrun iOS simulators. Use when attaching the Limrun Detox runtime to an app, wiring Detox mediator connectivity, or validating app/tester connections over destination tunnels.
user-invocable: true
---

# Limrun Detox

Use this for Detox runtime work on Limrun iOS. Keep build concerns separate
unless the user explicitly asks for a native build.

## Components

- Tester: local Node/Jest/Detox process.
- Mediator: `detox run-server`, usually local to the agent machine.
- App client: injected by limulator through `lim ios launch-app --runtime detox`.

## CLI Flow

Check current help before running commands you have not used in this session:

```bash
lim ios tunnel --help
lim ios launch-app --help
```

Run the long-lived mediator, tester, and tunnel from separate terminals.
Before using this quick path, ensure the project's `.detoxrc` reads the session
environment. Detox does not consume these variables automatically:

```js
session: {
  server: process.env.DETOX_SERVER || 'ws://localhost:8099',
  sessionId: process.env.DETOX_SESSION_ID || 'limrun-detox',
}
```

The complete configuration appears under **Detox Test Setup** below.

Terminal 1:

```bash
npx detox run-server -p 8099 -l verbose
```

Terminal 2:

```bash
lim ios tunnel \
  --selector localhost:8099 \
  --detach \
  --id <ios-id>
DETOX_SERVER_URL="ws://localhost:8099"
```

Terminal 3 starts the tester before the app connects:

```bash
DETOX_SERVER="ws://localhost:8099" \
DETOX_SESSION_ID=<session-id> \
  npx detox test --no-start
```

Then relaunch the app from Terminal 2. `--detox-version` is optional when
running from the project with `node_modules/detox`.

```bash
lim ios launch-app <bundle-id> \
  --id <ios-id> \
  --runtime detox \
  --detox-server-url "$DETOX_SERVER_URL" \
  --detox-session-id <session-id> \
  --detox-version <detox-version>
```

Prefer starting the tester before the app connects, or use the maintained orchestration in [limrun-inc/typescript-sdk `examples/detox-ios`](https://github.com/limrun-inc/typescript-sdk/tree/main/examples/detox-ios), to avoid benign mediator "cannot forward" noise.
If you manually launch the app before `npx detox test --no-start`, that mediator message is expected until the tester connects.

If tunnel start reports an active session, inspect it with `lim ios tunnel status --id <ios-id> --json`. Stop an obsolete session with `lim ios tunnel stop --id <ios-id>`, then start the declared mediator selector again.
An open idle tunnel does not count as instance activity, so it does not prevent
the simulator's inactivity timeout between test runs.

## Detox Test Setup

`npx detox test --no-start` still needs the normal Detox project configuration:

- Pass the Detox config file and configuration name from your project (see [`examples/detox-ios/.detoxrc.cjs` in limrun-inc/typescript-sdk](https://github.com/limrun-inc/typescript-sdk/blob/main/examples/detox-ios/.detoxrc.cjs) for a reference layout).
- Use the Limrun third-party driver: `type: '@limrun/detox/driver'`.
- Keep `DETOX_SERVER` and `DETOX_SESSION_ID` aligned with the mediator and launch command.
- Provide Limrun driver env such as `LIMRUN_IOS_ID`, `LIMRUN_IOS_API_URL`, and `LIMRUN_IOS_TOKEN` when screenshots or driver calls need the instance API.

Use [limrun-inc/typescript-sdk `examples/detox-ios`](https://github.com/limrun-inc/typescript-sdk/tree/main/examples/detox-ios) as the maintained happy path for exact config/env wiring. Use `-l trace` on `detox run-server` only when verbose logs are not enough.

For native SwiftUI apps, a minimal Detox configuration usually looks like:

```js
const server = process.env.DETOX_SERVER || 'ws://localhost:8099';
const sessionId = process.env.DETOX_SESSION_ID || 'limrun-detox';

module.exports = {
  testRunner: { args: { $0: 'jest' }, jest: { setupTimeout: 120000 } },
  session: {
    server,
    sessionId,
    debugSynchronization: 0,
  },
  apps: { ios: { type: 'ios.app', binaryPath: 'unused-by-limrun' } },
  devices: {
    limrun: {
      type: '@limrun/detox/driver',
      device: { id: process.env.LIMRUN_IOS_ID },
    },
  },
  configurations: {
    'ios.limrun': {
      device: 'limrun',
      app: 'ios',
      behavior: { init: { reinstallApp: false }, cleanup: { shutdownDevice: false } },
    },
  },
};
```

Then launch with `lim ios launch-app <bundle-id> --runtime detox ...` and run `npx detox test --no-start`.

## Validation Signals

- App connected: `detox run-server` logs `role:"app"` and `appConnected:true`.
- Tester connected: the same session reaches `testerConnected:true, appConnected:true`.
- Runtime loaded: the app connects to the mediator after the `--runtime detox` launch.
- UI visible: `lim ios element-tree --id <ios-id>` shows the expected app screen.

## Gotchas

- Do not pass arbitrary env vars, app args, or injectable paths. Use `--runtime detox`.
- `--detox-version` should match the local `detox` package version used by the tester. If omitted, `lim ios launch-app` resolves it from the current working directory; pass it explicitly when running outside the Detox project.
- Unsupported bundled Detox versions should fail with a clear supported-version list.
- `Cannot forward the message to the Detox client` can simply mean the app connected before the tester did.
- For SwiftUI, prefer stable accessibility identifiers, e.g. `.accessibilityIdentifier("greetingText")` with `by.id('greetingText')`; `by.text(...)` can miss labels that appear in `lim ios element-tree`.
- Debug failures by checking `lim ios element-tree --id <ios-id>` first, then mediator logs for app/tester connection state.
- Cleanup manual runs by stopping `detox run-server`, running `lim ios tunnel stop --id <ios-id>`, and deleting the instance with `lim ios delete <ios-id>` (`--id` is not valid for delete).
- This does not make Detox own the iOS lifecycle; prepare or reuse the Limrun instance separately.