iOS Simulator

Use Simulator as a reproducible verification environment while keeping device selection and destructive operations explicit.

Contents

• Scope and Safety
• Workflow
• Core Commands
• State and Diagnostics
• Recovery
• Verification Matrix
• iOS 27 Updates
• Common Mistakes
• Review Checklist
• References

Scope and Safety

This skill owns Simulator discovery, boot/shutdown, app install/launch, screenshots, logs, permissions, locations, push simulation, containers, and CI lifecycle. It does not replace real-device verification for hardware, performance, networking conditions, push delivery, camera, Bluetooth, NFC, or other device-only behavior.

Resolve an explicit simulator UDID before mutating state. Prefer an already booted suitable device. Do not erase or delete all simulators, broad CoreSimulator directories, or unrelated devices as a routine recovery step. If an erase/delete is genuinely needed, verify the exact target and preserve user data unless the task authorizes its removal.

Read simctl Command Reference for command syntax and less common operations.

Workflow

1. Inspect the Xcode project/workspace, scheme, supported platform, deployment target, installed runtimes, and available devices.
2. Select one destination by UDID and boot it if needed.
3. Build the intended scheme for that destination with a dedicated derived-data path when isolation helps.
4. Install and launch by bundle identifier; preserve the installed app container unless a clean-state test is required.
5. Capture logs, screenshots, and interaction evidence relevant to the request.
6. Clean up only devices, overrides, permissions, locations, or temporary artifacts created for the task.

Core Commands

xcrun simctl list devices available
xcrun simctl bootstatus <UDID> -b
xcodebuild -project App.xcodeproj -scheme App \
  -destination 'platform=iOS Simulator,id=<UDID>' build
xcrun simctl install <UDID> /path/to/App.app
xcrun simctl launch <UDID> com.example.app
xcrun simctl io <UDID> screenshot /tmp/app.png

Use parsed command output or an explicit known UDID. Do not hardcode a device name when multiple runtimes can contain the same name.

State and Diagnostics

• Reinstalling over an app normally preserves its data; uninstalling or erasing does not.
• Use get_app_container before inspecting sandboxed files.
• Prefer subsystem/category log predicates over unfiltered log streams.
• Clear status-bar, location, appearance, and permission overrides after tests that change them.
• Push simulation validates payload handling in Simulator, not production APNs delivery.
• Permission grants are useful in CI; permission behavior itself needs dedicated denied/limited/authorized tests.

Recovery

When launch or boot fails, inspect device state and the exact error first. Try the narrowest recovery: terminate the app, relaunch, shut down the chosen simulator, or recreate only the disposable device created for the task. Treat erase/delete as destructive and target a validated UDID.

Do not present broad cache deletion or erase all as a default fix. Stop and report when recovery would remove user-owned simulator data outside the requested scope.

Verification Matrix

Choose checks proportional to the change:

• build success and clean diagnostics
• cold/warm launch
• persistence across relaunch
• target appearance and Dynamic Type size
• required permission states
• screenshots of important states
• focused logs for crashes or runtime warnings
• real-device follow-up for unsupported hardware behavior

iOS 27 Updates

• simctl and devicectl can reboot simulators. Runtimes ship a pre-built dyld cache for faster first launch.
• Device Hub supports network pairing and mouse/trackpad gestures in simulators; these generate UIKit scroll, transform, and pointer events and do not match physical devices.
• devicectl JSON output version 5 deprecates hardwareProperties, deviceProperties, and connectionProperties in favor of properties.
• Known issue (27.2): cloning a 27.2 runtime simulator may fail due to file permissions.
• Agents in Xcode 27 can boot simulators, install and launch apps, and capture screenshots.

Sources: https://sosumi.ai/documentation/xcode-release-notes/xcode-27-release-notes, https://sosumi.ai/documentation/ios-ipados-release-notes/ios-ipados-27_2-release-notes

Common Mistakes

• Hardcoding device names instead of targeting explicit simulator UDIDs.
• Assuming APNs remote push behavior in Simulator is identical to production hardware.
• Executing erase all or deleting CoreSimulator folders as a default troubleshooting step.
• Leaving override states (status bar, location, appearance) active after test execution.
• Testing Bluetooth Low Energy or camera capture on Simulator without mocked data or fallback.

Review Checklist

• Project, scheme, runtime, target, and bundle identifier are resolved
• Commands target an explicit UDID
• Existing app data is preserved unless clean state is required
• Screenshots and logs correspond to the tested build
• Overrides and task-created devices are cleaned up narrowly
• No broad erase/delete operation targets unrelated simulator data
• Simulator-only results are not claimed as real-device proof
• CI-created devices have deterministic teardown

References

• Complete simctl command reference