Testing

The testing skill provides knowledge for writing and running UI test flows for React Native feature verification. Covers test runner selection, timing rules, flow structure, multi-device testing, auth pre-flight, and permission handling.

When loaded

Activates when Claude encounters tasks involving Maestro tests, E2E flows, testIDs, UI test execution, network mocking, store state inspection, or test assertions.

Key Knowledge Areas

Test Runner: maestro-runner (preferred)

A Go-based drop-in replacement for Maestro with the same YAML syntax:

Metric	Maestro (Java)	maestro-runner (Go)
Binary size	~300MB (with JVM)	21MB
Startup time	2-4s	<100ms
Memory	~400MB	~30MB
Flow execution	Baseline	2-3x faster

Critical Timing Rule

After any UI interaction, React needs time to commit updates to the fiber tree.

Correct sequence:

1. device_find / Maestro tap
2. device_snapshot / Maestro assertVisible (wait for settle)
3. cdp_store_state (now safe to read)

Wrong (race condition): tapping then immediately querying CDP returns stale state.

Optimized Test Loop

Per-step timing with maestro-runner + JPEG: ~1.4s (2.2x faster than Maestro + PNG baseline of ~3.1s).

Maestro Flow Patterns

• Basic structure: appId header + step list
• Never use clearState: true with Expo Dev Client (wipes Metro URL)
• Navigation via deep links or testID taps
• Assertions: assertVisible, assertNotVisible, text content matching

testID Conventions

• Stable semantic names: add-to-cart-btn, cart-badge, search-input
• Dynamic IDs for list items: testID={`product-item-${item.id}`}
• Every Pressable, TouchableOpacity, Button, TextInput, and scrollable container must have a testID

Component Tree Token Efficiency

• Never call cdp_component_tree without a filter parameter (full dumps produce 10K+ tokens)
• Fiber tree presence does not mean screen visibility

Auth Pre-flight

Before testing, checks cdp_navigation_state for auth screens. If logged out:

1. Scans for Maestro subflows (prefer login over registration)
2. Strips clearState: true for Dev Client builds
3. Wraps subflows with appId if missing
4. Runs via maestro-runner, verifies arrival at main screen

Permission Pre-flight

For permission-gated flows, queries and sets the correct state:

Platform	Query	Grant	Revoke	Reset
Android	dumpsys	pm grant	pm revoke	pm reset-permissions
iOS Sim	Not supported	simctl privacy grant	simctl privacy revoke	simctl privacy reset

Network Mocking

Injects mocks via cdp_evaluate using global.__RN_AGENT_MOCKS__ before navigating to the screen under test.

Zustand Store Inspection

Zustand v4+ uses useSyncExternalStore (not React Context), so fiber tree walking cannot detect stores. Projects must register store hooks:

if (__DEV__) {
  global.__ZUSTAND_STORES__ = {
    auth: useAuthStore,
    cart: useCartStore,
  };
}

Then cdp_store_state(path="cart.items") reads the live state.