Interview questions in Mobile Dev, page 26
Automatic signing: benefits and limitations on teams
Automatic signing creates certificates and profiles on demand and keeps them in sync, easing local setup; limits include proliferating certificates, weak CI fit, and less control for complex entitlements.
Testing a tap that triggers a SnackBar
PumpWidget the app, find the button, tester.tap it, call pump or pumpAndSettle to advance frames, then expect a SnackBar finder.
What is the role of TestDispatcher and runTest in coroutine testing?
This tests coroutine test infrastructure and virtual time control. A great answer says runTest installs a TestDispatcher and TestScope, skips delays automatically, and exposes advanceTimeBy to test timeouts instantly.
RNTL or Detox for a navigation flow?
RNTL can test navigation logic by rendering the navigator in JS and asserting screen changes; Detox runs the real app for true end-to-end confidence including native transitions.
App Thinning: slicing, bitcode, and on-demand resources
Slicing delivers only the assets and code a device needs; bitcode let Apple recompile and re-optimize; on-demand resources defer large assets until requested.
How do you diagnose and fix flaky Flutter widget tests?
Audit unawaited futures, swap pumpAndSettle for explicit pumps or mock timers, and reproduce with logs.
What is Android Test Orchestrator and how does it isolate tests?
Tests process-level isolation in Android UI suites. A strong answer says it runs each test in its own Instrumentation process, stopping crashes or leaked state from cascading, and notes slower startup.
What are the key challenges of setting up Detox E2E?
Maintain separate debug/release build configs, rely on Detox automatic synchronization but tame uncontrolled async like timers and animations, and stabilize CI with headless emulators and retries.
Securely managing signing assets in CI/CD
Keep encrypted certificates and profiles in a controlled store or fastlane match repo, inject the decryption key and credentials via CI secrets, install into a temporary keychain per run.
Flutter command for an Android release build and APK vs AAB difference.
Flutter CLI release commands and Android distribution formats. Name flutter build apk and flutter build appbundle; note AAB lets Google Play generate optimized APKs per device while APK is a single direct-install file.
What is an Android memory leak? Give a Context example and fix.
Tests understanding of Activity Context retention preventing GC. A strong answer defines a leak as unreachable objects, gives a static singleton example, names LeakCanary, and fixes it with Application Context. Red flag: blaming GC or suggesting System.gc().
How do you catch RN performance regressions?
Track TTI, JS and UI thread FPS, and memory; baseline them and gate CI with automated tools like Flashlight, using the React profiler and DevTools to diagnose.
Privacy manifests and the app privacy report
PrivacyInfo.xcprivacy declares collected data types, tracking, and reasons for required-reason APIs; Xcode aggregates your manifest plus SDK manifests into a privacy report.
How would you manage different backend environments in a Flutter project?
Tests Flutter build flavors and compile-time config injection. A strong answer uses dart-define or flavor-specific entry points plus an EnvironmentConfig abstraction. A red flag is manually swapping hard-coded base URLs before each build.
What is overdraw in Android UI and how do you reduce it?
This tests GPU fill awareness. A strong answer defines overdraw as redrawing pixels repeatedly, names Debug GPU Overdraw's color overlay, and offers fixes: remove unnecessary backgrounds and flatten hierarchies. Red flag: confusing this with CPU layout issues.
iOS Provisioning Profiles and Signing Certificates
The certificate proves developer identity, the App ID names the app, the profile binds certificate, App ID, and devices.
Purpose and setup of an Objective-C bridging header
The bridging header imports ObjC headers into Swift; Xcode auto-creates it or you add it manually and set the build setting.
iOS code signing for a TestFlight release
A signing certificate proves who built the app; a provisioning profile ties cert, app ID and devices together; configure in Xcode, archive and upload.
Why avoid plain SharedPreferences for secrets and what to use?
Tests data-at-rest security awareness. A strong answer notes plain SharedPreferences writes unencrypted XML that rooted users or backups expose, then names EncryptedSharedPreferences with Android Keystore.
Managing Per-Environment Configuration in React Native
Use per-environment env files plus build flavors or schemes, inject at build time, keep secrets off the device.
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