Interview questions in Mobile Dev, page 25
App ID, provisioning profile, and signing certificate
The certificate proves who you are, the App ID identifies the app and its capabilities, and the provisioning profile binds certificate, App ID, and allowed devices so iOS trusts the install.
What is Pigeon and how does it improve platform channels?
This tests type-safe platform channels versus manual MethodChannel boilerplate. Answer: Pigeon is a dev-time code generator that creates typed host stubs from a Dart contract, removing string keys and encoding. Red flag: calling it a runtime library.
Unit test a ViewModel exposing StateFlow in a local JVM test
Tests coroutine hygiene and flow collection strategy. A strong answer covers injecting a TestDispatcher, using runTest, collecting emissions in a background scope, and asserting states.
Why use a C++ TurboModule, and what are the risks?
C++ JSI bindings give synchronous, serialization-free calls and shared cross-platform code; challenges are manual memory ownership across the JS-C++ boundary, GC interaction, and thread safety.
Archiving and uploading a build to TestFlight
Select a real-device or Any iOS destination, Product Archive, then in the Organizer distribute to App Store Connect, where the build appears for internal TestFlight testers after processing.
Unit, widget, and integration test differences in Flutter
Tests your grasp of Flutter's test pyramid and isolation levels. Unit tests check pure Dart logic; widget tests verify UI in a headless environment; integration tests exercise the full app on a device. Red flag: saying widget tests require an emulator.
Explain integration tests and isolate Room DAO tests
Tests integration vs unit testing and Room isolation. Outline: verify real DAO-to-DB interaction with Room.inMemoryDatabaseBuilder; reset state by closing and recreating the DB in @After. Red flag: mocking the DAO or using an on-disk database.
Unit testing vs component testing in React Native
Unit tests verify isolated functions/logic with Jest; component tests render components and assert behavior with React Native Testing Library.
Ad Hoc versus external TestFlight distribution
Ad hoc installs on pre-registered device UDIDs without Apple review; external TestFlight reaches many testers via the app but needs Beta App Review.
How do you verify a Text widget with 'Hello' is present?
Find.text('Hello') locates the widget; expect(finder, findsOneWidget) asserts exactly one exists.
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.
How do you mock a fetch call in Jest tests?
Replace global fetch with a Jest mock or a library like jest-fetch-mock, return a resolved Promise with a fake Response, and reset mocks between tests.
Using dSYM files to symbolicate crash reports
A dSYM maps stripped memory addresses back to function names, files, and line numbers; matched by UUID it symbolicates the report to readable frames.
How do you widget-test states without real network calls?
This tests UI isolation from I/O. Mock the repository with Mockito, stub methods to yield loading, success, and error, and inject it via constructor or provider. Avoid real HTTP calls or unmocked clients in widget tests.
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.
How do you test a component using a native module?
Native code is absent in the Node-based Jest environment, so you mock the module with jest.mock to return fake values, often via the library's provided jest mock.
Phased release to limit update risk
Enable phased release so an approved update reaches a growing percentage of automatic-update users over seven days; pause if metrics spike.
Unit test a BLoC handling an AddItem event and emitting state
Use blocTest with build, act, expect; mention seed, skip, and mocktail for dependencies.
How would you implement and register a custom IdlingResource?
Implement the three IdlingResource methods with an atomic counter; register via IdlingRegistry in setup and unregister in teardown.
What does 'test behavior, not implementation' mean?
Query elements the way a user finds them (text, role, label) and assert observable behavior; for a Button, fire press and assert the visible effect, not internal state.
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