Describe a robust error handling strategy for network requests
Tests whether you classify failures by layer rather than catching everything generically. Inspect DioExceptionType for connectivity, check HTTP status before parsing, and isolate JSON decode errors. Never show the same message for timeouts and 500s.
Difference between context.watch, context.read, and Selector in Provider and Riverpod
Tests rebuild granularity in Flutter. A strong answer distinguishes listening versus one-time lookup, explains that Selector filters rebuilds by comparing sub-values, and warns that context.read inside build causes missed updates.
Implement efficient async username validation in Flutter
Tests async field hygiene in Flutter. Outline: debounce 300ms, cancel inflight requests, decouple loading UI from errors, use reactive_forms async validators or manual streams. Red flag: API calls per keystroke without cancellation, loading treated as errors.
How do you split a Column 1/3 and 2/3 using Expanded?
Tests understanding of flex allocation in Flutter layouts. Strong answers wrap both containers in Expanded, assign flex values of 1 and 2, and note that Expanded forces children to fill the Column's main axis. Red flag: proposing fixed heights instead of flex.
Describe the Dart event loop and queue execution order
Tests your grasp of Dart's single-threaded event loop priority. Great answers state: microtasks drain fully before the next event processes, cycling forever. Red flag: saying Future and scheduleMicrotask interleave in call order.
Explain Dart's event loop, microtask queue, event queue, and await behavior
Tests Dart single-threaded event loop model. Strong answer: microtasks drain before event queue tasks; await suspends the function and schedules its resumption via the event loop when the Future completes. Red flag: claiming await blocks the thread.
Describe Dart's null-aware ?. and null assertion ! operators
Tests Dart null safety mechanics: ?. short-circuits member access on null, while ! casts away nullability. A strong answer notes ?. avoids NPEs and ! is a risky opt-out. Red flag: claiming ! is safe or that ?. provides a default value.
Explain R8's shrinking, obfuscation, and optimization phases and how to influence optimization
WHAT IT TESTS: Whether you understand R8 beyond a black box. ANSWER OUTLINE: Separate dead code removal, renaming, and bytecode transformation; cite ProGuard keep rules and selective passes. RED FLAG: Thinking optimization is only the minifyEnabled toggle.
Google Play App Signing: upload key versus app signing key
Tests Android signing infrastructure and key escrow knowledge. A strong answer states Google holds the app signing key while you retain an upload key, protecting critical signing material. Red flag: claiming both keys sign the final install artifact.
Purpose of Android app signing and keystore contents
WHAT IT TESTS: App identity on Android. ANSWER OUTLINE: Signing proves authorship and integrity, enables same-key updates, and binds app identity; a keystore holds private keys and certificates.
How would you use Perfetto and Trace.beginSection to find a non-obvious bottleneck?
Tests correlation beyond CPU sampling. Covers coarse Trace.beginSection to limit 1-10us overhead, recording app ATrace with CPU/scheduling tracks, and correlating slices against scheduler latency. Red flag: omitting overhead or ignoring Perfetto SQL queries.
Explain generational GC in ART and why onDraw must avoid allocations
WHAT IT TESTS: ART generational GC and onDraw allocation hazards. ANSWER OUTLINE: Covers young-gen nursery, mark-sweep fallback, and why a 5-10ms GC pause misses 16ms frame deadline. RED FLAG: Blaming GC without linking allocation to frame timing.
Use Android Keystore to secure a database encryption key
Tests Android Keystore key generation and hardware trust boundaries. Strong answers: KeyGenParameterSpec with AES/GCM, TEE vs StrongBox isolation, setIsStrongBoxBacked on API 28+ with fallback, wrapping the database key. Red flag: claims Keystore encrypts DBs.
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.
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().
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 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.
How would you implement and register a custom IdlingResource?
WHAT IT TESTS: Whether you know Espresso's async contract. ANSWER OUTLINE: Implement the three IdlingResource methods with an atomic counter; register via IdlingRegistry in setup and unregister in teardown. RED FLAG: Suggesting Thread.sleep or polling loops.
How do you test a Compose click and verify state change?
This tests Compose semantics and interaction-to-assertion flow. Mention ComposeTestRule, onNodeWithTag, performClick, and assert on the changed node with assertIsDisplayed or assertTextEquals.
Mock vs Fake test doubles: when to use a Fake Repository?
Tests if you know a Fake is a working lightweight implementation while a Mock verifies interactions. Good answers define Fake as in-memory with real logic, Mock as expectation-based, and choose a Repository Fake when many tests need reusable state.