Generating a signed release APK or AAB
WHAT IT TESTS: Android release signing. OUTLINE: create a keystore, reference its credentials via gradle.properties (gitignored), wire a release signingConfig in build.gradle, then assembleRelease or bundleRelease.
Fabric UI update lifecycle vs old architecture
WHAT IT TESTS: the Fabric render pipeline. OUTLINE: render builds an immutable C++ shadow tree, commit diffs trees and runs Yoga layout, mount applies mutations to native views; JSI shares the tree, enabling synchronous and concurrent rendering unlike the…
TurboModule lazy loading vs eager startup
WHAT IT TESTS: why lazy module init speeds startup. OUTLINE: legacy modules are instantiated eagerly at launch; TurboModules initialize only when JS first accesses them, so unused modules cost nothing at startup.
What JSI is and how it replaces the Bridge
WHAT IT TESTS: understanding JSI fundamentals. OUTLINE: JSI is a lightweight C++ layer letting JS hold references to native host objects and call them directly and synchronously, with no JSON serialization or async batched queue.
TurboModules and lazy loading benefits
WHAT IT TESTS: new-architecture native modules. OUTLINE: TurboModules use JSI for direct, synchronous, type-safe calls and are loaded lazily on first use instead of all at startup, cutting init time.
Threading of native module methods
WHAT IT TESTS: native module threading. OUTLINE: methods run on a dedicated native module queue, not the UI thread; long blocking work stalls other module calls; offload to a background executor or override methodQueue, returning results via promise.
Purpose of RCTBridgeModule and ReactContextBaseJavaModule
WHAT IT TESTS: understanding the native module contract. OUTLINE: these declare a class as a discoverable native module, provide the JS-facing name, and let RN export methods to JavaScript.
Creating a native module with a sync method
WHAT IT TESTS: native module mechanics across platforms. OUTLINE: extend the RN base class, mark the method exported and synchronous, register in a package or bridging file.
Offline data storage and sync strategy
WHAT IT TESTS: offline-first design. OUTLINE: persist locally in SQLite or WatermelonDB, queue mutations with a pending flag, detect reconnection with NetInfo, then replay the queue and resolve conflicts.
Unifying divergent native video player props
WHAT IT TESTS: designing a cross-platform wrapper over divergent native views. OUTLINE: a JS component accepts a unified source prop, then uses Platform.OS to map it into each native view's expected props before rendering.
Platform-specific typography in a global theme
WHAT IT TESTS: centralizing platform-aware styling. OUTLINE: define one theme with Platform.select for fontFamily, expose semantic text styles, and reuse them everywhere rather than per-screen overrides.
Android-only native module called safely from JS
WHAT IT TESTS: building a platform-specific native module and guarding calls. OUTLINE: write a ReactContextBaseJavaModule with an exported method, register it in a package, then guard the JS call with Platform.OS or a null check on the module.
Passing params between Stack Navigator screens
WHAT IT TESTS: navigation params basics. OUTLINE: navigate to the route with a params object, read it via route.params on the target, pass an id not a huge object. RED FLAG: using global state or refs to smuggle data instead of route params, or passing.
Composing tap and pan gestures together
WHAT IT TESTS: gesture composition and relations. OUTLINE: declare both gestures and relate them with simultaneous or exclusive composition, using Gesture.Race or simultaneousHandlers so a small move stays a tap.
Adding native code to Expo without ejecting
WHAT IT TESTS: knowing modern Expo CNG and dev clients. OUTLINE: use prebuild with config plugins to inject native changes, build a custom development client with EAS, keep native folders generated not hand-edited.
The legacy React Native Bridge architecture
WHAT IT TESTS: knowing the old three-thread Bridge model. OUTLINE: JS, native, and shadow threads communicate via an async, batched, JSON-serialized Bridge. RED FLAG: calling the Bridge synchronous, ignoring serialization cost, or confusing it with JSI.
Web DOM elements vs React Native core components
WHAT IT TESTS: understanding RN renders to native views, not the DOM. OUTLINE: View maps to UIView/ViewGroup, Text to native text, no HTML or CSS, all text must be inside Text. RED FLAG: claiming RN runs in a webview or uses real div and CSS.
Build flavors and schemes for RN environments
WHAT IT TESTS: managing dev, staging, and prod builds natively. OUTLINE: Android productFlavors with distinct applicationId and resources, iOS schemes plus configurations and targets, environment config injection.
Layered testing strategy for a large RN app
WHAT IT TESTS: understanding the test pyramid in RN. OUTLINE: many fast Jest unit tests, fewer RNTL component tests on behavior, few Detox/Maestro E2E on critical flows.
Unit testing a custom hook with renderHook
WHAT IT TESTS: knowing how to test hook logic in isolation. OUTLINE: render the hook, read result.current, fire actions inside act, assert updated state. RED FLAG: calling hook directly outside a component or skipping act around updates.