android-testing

Android Testing Standards

Priority: P0 (CRITICAL)

The Four-Pillar Test Value Framework

Qualitative reasoning framework to evaluate unit test value:

• Protection against Regressions: Catches real defects; a test passing during failure offers zero protection.
• Resistance to Refactoring: Decoupled from internal implementation; zero false alarms on internal refactorings.
• Fast Feedback: Executes in milliseconds; rapid local TDD feedback loop.
• Maintainability: Clean AAA structure, high readability, zero boilerplate duplication. Avoid inventing arbitrary numeric scores (e.g. P * R * F * M) statically without empirical measurement.

Core Rule Anchors

• [MOB-TEST-01] Tripartite Naming: Name tests Method_Scenario_ExpectedBehavior (e.g. submitOrder_whenCreditLimitExceeded_displaysBlockedBanner).
• [MOB-TEST-02] State & ViewModel Invariant Rule: Assert UI state transitions (e.g. StateFlow/UiState via Turbine test {}); ban asserting 30-property boilerplate state copies.
• [MOB-TEST-03] Entity Invariant & Serialization Rule: Test calculations, validations, domain invariants, and non-trivial serialization/parsing or error mapping. Ban testing auto-generated code, trivial getters, or echo tests repeating literal assignments.
• [MOB-TEST-04] Contract Testing Rule: Repositories and data sources must be tested for contract compliance and error mapping. Ban 1:1 pass-through mock echoing (coEvery { dataSource.get() } returns x; repo.get() == x).
• [MOB-TEST-05] Bug-First Regression Lock: Every PR fixing a bug ticket or with title fix(...) must introduce a failing test reproducing the defect before fixing it.

Implementation Guidelines

Unit Tests

• Scope & Async: ViewModels, Usecases, Repositories, Utils. Use runTest with MainDispatcherRule. Mock with MockK or fakes.
• Coverage: Coverage is diagnostic and project-configured; verify risk-weighted critical paths rather than padding code for an arbitrary percentage.

UI Integration Tests (Instrumentation)

• Scope & DI: Composable Screens, Navigation flows. Use createAndroidComposeRule + Hilt (HiltAndroidRule). Fake repositories via @TestInstallIn.
• Negative Assertions: Add negative assertions only when absence is part of the business contract.

Anti-Patterns & Banned Smells

• [MOB-TEST-01] Vague names: Banish non-descriptive test names.
• [MOB-TEST-02] Brittle state copies: Ban asserting 30-property boilerplate state copies; use focused state assertions or Turbine.
• [MOB-TEST-03] Echo tests: Ban testing auto-generated code, trivial getters, or repeating literal assignments.
• [MOB-TEST-04] Pass-through mock echoing: Ban 1:1 pass-through mock echoing and shallow assertions without contract checks.
• [MOB-TEST-05] Missing bug reproduction: Ban bug fix PRs without reproduction tests.
• No Real Network / Thread.sleep: Fake repositories in DI; use IdlingResource or composeTestRule.waitUntil for async timing.

References

• Test Rules