Maestro mobile E2E testing patterns for React Native/Expo apps: YAML test flows, testID selectors, adaptive auth state, optimistic update verification, GraalJS scripting, cross-platform stability, CI/CD integration, Maestro Cloud, and MCP server integration

Maestro Mobile E2E Testing Overview Maestro is a declarative YAML based mobile E2E testing framework. It provides automatic waiting, built in retry logic, and fast execution without boilerplate. It's more stable than Detox or Appium for React Native apps. Key Features Declarative YAML — no imperative test code, just steps Automatic waiting — no manual sleep() or flaky waits Built in retry — reduces test flakiness Fast execution — runs quickly without setup overhead Maestro Studio — interactive test builder ( maestro studio ) Sub flows — reusable YAML sequences for DRY tests JavaScript scripting — GraalJS runtime for HTTP calls and data manipulation Maestro Cloud — real device testing in CI without local simulators Quick Start Install Minimal test Run Core Patterns 1. Selector Strategy: testID vs Text Choose your selector approach based on project context. Both are valid — the right choice depends on whether your app is localized and your team's testing philosophy. Context Recommended Selector Rationale Multi language / i18n id: (testID) Stable across translations Single language Text labels Human readable, self documenting tests Agent maintained tests Either — ask the developer Readability matters less for AI maintained flows System dialogs Text (always) No testID possible on native alerts When to prefer testIDs: App supports multiple languages or will be translated UI text is dynamic or frequently changes Multiple elements share the same visible text When to prefer text selectors: Single language app with stable copy Readability and self documentation are a priority Testing user visible behavior exactly as it appears In React Native, add testID props when using ID based selectors: testID Naming Convention When using ID based selectors: 2. Auth Pre Flight Pattern Prevent race conditions where Maestro interacts with the UI before auth state resolves. Add a zero size auth loaded marker that only renders when auth loading completes: Then in every test: 3. Adaptive Tests (Handle Both Auth States) Tests should work regardless of whether the user is authenticated: 4. Testing Optimistic Updates Use short timeouts to verify UI changes happen before server response: Action Expected Change Timeout Mutation trigger Button state flips < 3s List update Item appears/disappears < 5s Re do action Proves persistence < 3s 5. Dismissing Native Alerts React Native Alert.alert() creates native dialogs that block the UI: 6. Sub Flows for Reusability Break repeated sequences into sub flow files: 7. Deep Links (Expo) Use the Expo scheme from app.json , not the bundle ID: Deep links must be registered in your app's deep link handler. Unregistered routes silently fail. 8. Platform Specific Logic 9. Environment Variables 10. Selector State Properties Use enabled , selected , checked , and focused to target elements by their current state. This is useful for validating interactive element states before or after actions. Property Values Use Case enabled true / false Buttons that disable during submission or until form is valid checked true / false Checkboxes, toggle switches selected true / false Tab items, segmented controls focused true / false Input fields with auto focus 11. Relative Position Selectors Distinguish between similar elements by their spatial relationship to other elements. This is more idiomatic and resilient than index based selection. Available relative selectors: Selector Meaning below: Element is positioned below the referenced element above: Element is positioned above the referenced element leftOf: Element is to the left of the referenced element rightOf: Element is to the right of the referenced element childOf: Element is a direct child of the referenced parent containsChild: Element contains a direct child matching the reference containsDescendants: Element contains all specified descendant elements Authentication Testing Architecture Testing OTP or magic link authentication in E2E requires capturing emails programmatically. The general pattern: Common email capture services: [Mailpit](https://github.com/axllent/mailpit), [MailHog](https://github.com/mailhog/MailHog), [Ethereal](https://ethereal.email/). OTP Fetch Script Fetch OTP codes from your email capture service using Maestro's GraalJS runtime: OTP Input Strategy OTP components with auto focus need individual digit entry. Tap each input before typing: For provider specific implementations (Supabase + Mailpit, Firebase Auth, Auth0), create a project level skill that extends this one. GraalJS Script Rules Maestro uses the GraalJS runtime. These constraints are non negotiable: Feature Status async/await NOT supported fetch() NOT supported http.get() , http.post() Use these instead json() Use to parse response bodies output.VAR Set variables for use in YAML flow var declarations Required (use var , not const / let for safety) Critical Gotchas clearState Does NOT Clear iOS Keychain clearState: true clears the app sandbox (UserDefaults, files, caches) but does NOT clear the iOS Keychain. Auth tokens stored via expo secure store (or any Keychain based storage) persist across clearState resets and even app reinstalls. Rules: Never rely on clearState to produce guest state on iOS For auth tests: skip clearState , use auth loaded pre flight For guest tests: use adaptive flows that handle both states Never assert guest only UI after clearState Note: On Android, clearState: true fully resets app data including credentials. This is an iOS only gotcha. XCTest kAXErrorInvalidUIElement Crash (iOS) The XCTest driver may crash if Maestro interacts with the accessibility tree before the first render cycle completes on cold boot. Fix: Add a no op swipe immediately after launchApp : API Server Dependency Mobile apps calling backend APIs on localhost need either the full server or a mock server running. Without it, all API dependent screens show loading spinners or empty states (queries fail silently). Fix: Start a mock API server before running Maestro tests: Create a lightweight mock that returns canned JSON for each endpoint your app calls. This is faster and more deterministic than running your full backend. Auth Aware Tab Bars Tab bars that show different tabs for guest vs authenticated users will cause selector failures: State Typical Tabs Guest home, search, cart, profile Auth home, feed, create, messages, profile Only assert tabs that exist in both states, or use adaptive when: conditions. Test File Template Folder Structure Naming Conventions Type Pattern Example Main test {feature} {action}.yaml checkout purchase.yaml Sub flow {action} {context}.yaml auth and return to dashboard.yaml Script {verb} {noun}.js fetch otp.js Infrastructure Mock Server for API Dependent Tests Create a lightweight mock server that serves canned responses for your API layer. This is faster and more deterministic than running your full backend during E2E tests. Orchestration Script Automate the full E2E setup with a shell script that: 1. Starts backend services (database, auth) 2. Seeds test data 3. Starts mock API server 4. Runs Maestro tests 5. Cleans up all services Seed Data Tests that depend on specific data require seeded databases. Keep seed scripts alongside your test infrastructure and run them before each test suite. Android Specific Patterns Emulator Setup Android tests require an emulator or a USB connected physical device. Maestro auto detects connected devices. iOS vs Android Differences Aspect iOS Android Device type Simulator only (no physical) Emulator + physical via ADB clearState Does NOT clear Keychain Fully resets app data Cold boot crash XCTest kAXError (add swipe delay) No equivalent issue Performance Runs natively (fast) ARM emulation (slower on x86) Permission dialogs System alerts System dialogs with different text ADB Debugging Android Permission Handling Android permissions appear as system dialogs. Dismiss with optional taps: CI/CD Integration GitHub Actions with Maestro Cloud Maestro Cloud provides real devices in CI without local simulators. Use the official action: Tag Based Flow Filtering Use tags to control which tests run in CI vs locally: Local CI with Docker (Android Only) Note: iOS tests cannot run in Docker (requires macOS). Use Maestro Cloud for iOS in CI. Maestro Cloud [Maestro Cloud](https://cloud.maestro.dev/) runs tests on real devices without local simulator setup. Setup 1. Create account at cloud.maestro.dev 2. Generate API key from dashboard 3. Store as MAESTRO API KEY secret in your CI provider Running from CLI Key Points iOS testing : Supported on Maestro Cloud (not on local physical devices) Android testing : Both local physical devices and Maestro Cloud Results : Dashboard with video recordings, logs, and screenshots CI outputs : MAESTRO CLOUD CONSOLE URL , MAESTRO CLOUD FLOW RESULTS Maestro MCP Server The [Maestro MCP server](https://docs.maestro.dev/getting started/maestro mcp) exposes Maestro's full command set as Model Context Protocol tools, letting AI agents execute tests and interact with devices directly — not just write YAML. How It Complements This Skill This Skill Maestro MCP Role Teaches correct patterns Provides runtime execution Layer Authoring (write good YAML) Execution (run, tap, assert, screenshot) Output Better test files Live device interaction Use both together: this skill ensures the AI writes correct tests; the MCP lets it run them immediately, see failures, and iterate. Setup The MCP ships with the Maestro CLI — no extra install needed: Claude Code — add to project .mcp.json or global settings: Claude Desktop — add to ~/Library/Application Support/Claude/claude desktop config.json (macOS): Also supported on Cursor, Windsurf, VS Code, and JetBrains IDEs. See the [Maestro MCP docs](https://docs.maestro.dev/getting started/maestro mcp) for IDE specific setup. Key Capabilities The MCP server exposes 47 tools organized by category: Category Tools Examples UI Interaction tap, swipe, scroll, long press tapOn , scrollUntilVisible Text Input type, erase, paste, copy inputText , eraseText Assertions visibility, AI powered assertVisible , assertWithAI App Lifecycle launch, stop, clear state launchApp , clearState Device Control location, orientation, airplane setLocation , hideKeyboard Flow Control run flows, repeat, eval scripts runFlow , evalScript Media screenshots, recording takeScreenshot , startRecording AI Powered visual assertions, defect detection assertWithAI , assertNoDefectsWithAI Write Run Fix Loop With both this skill and the MCP active, the AI can: 1. Write a test YAML using patterns from this skill 2. Run it via MCP's runFlow / launchApp + interaction tools 3. See failures via screenshots and assertions 4. Fix the YAML and re run — all in one conversation Debugging Screenshots saved to ~/.maestro/tests/{timestamp}/ . Checklist for New Tests Common Errors Error Cause Fix "Unable to locate Jav

maestro-mobile-testing