applying-testing-strategies

Use Given-When-Then as inline comment blocks separating setup, action, and assertion phases within each test method. Google's official samples use this comment style, though no documentation page formally prescribes it; pick one vocabulary per repository and apply it consistently.

Use @UninstallModules on the test class to remove the production module, then provide a replacement via an inner @Module or a @BindValue field. For replacements applying to all tests in a module, use @TestInstallIn with the replaces attribute instead.

The usual cause is non-determinism from wall-clock time, real dispatchers, animations, or external state like network and unseeded Random. Inject a Clock and DispatcherProvider, seed Random, set testOptions.animationsDisabled = true, and clear app state before instrumented tests.

HiltAndroidRule must execute before any rule that touches the injected graph, such as ActivityScenarioRule or composeTestRule. The conventional pattern is @get:Rule(order = 0) on HiltAndroidRule and order = 1 on the next rule, though any monotonic ordering with Hilt first works.

Backtick test names in instrumented tests are only supported on devices running API 30 and above. Local JVM tests can use backticks freely; for instrumented tests targeting lower API levels, use camelCase or snake_case names like loadUsers_emptyList_emitsEmptyState.

Hilt is unnecessary for local unit tests of classes using constructor injection — instantiate the class directly with fakes. Reserve @HiltAndroidTest for UI and integration tests where Hilt generates components and injects dependencies as in production.