Write unit tests for FocusManagementService
epic-screen-reader-support-core-services-task-012 — Use the AccessibilityTestHarness to write comprehensive unit and widget tests for FocusManagementService. Cover: focus lands on correct element after route push, focus restores after route pop, focus moves to dialog on open, focus restores to trigger on dialog close, and moveFocusTo handles unmounted targets gracefully. Achieve ≥90% branch coverage on the service.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 3 - 413 tasks
Can start after Tier 2 completes
Implementation Notes
FocusManagementService likely maintains an internal stack of FocusNodes for history-based restoration. Write a test helper function buildTestRoute(harness, {FocusNode? autoFocusNode}) that creates a simple page widget which auto-focuses the given node on mount — this eliminates boilerplate across tests. For the unmounted target test, build a StatefulWidget that removes the target from the tree (setState removes a conditional child) before calling moveFocusTo — this reliably reproduces the unmounted case.
Use debugFocusTree() output in test failure messages to aid diagnosis. If FocusManagementService is a Riverpod provider, override it in tests using ProviderScope(overrides: [...]) with a real (not mocked) instance to test actual behaviour rather than mock behaviour.
Testing Requirements
Pure flutter_test suite. Organise tests in describe-style groups: 'route navigation focus', 'dialog focus', 'edge cases'. Use testWidgets for all tests requiring a widget tree. For each test, build a minimal widget tree via AccessibilityTestHarness that reproduces exactly the scenario being tested — avoid reusing complex production screens to keep tests fast and isolated.
Use expect(tester.semantics, ...) matchers where available for focus assertions, or check FocusNode.hasFocus directly after pumpAndSettle. Document each test with a one-line comment explaining which branch of FocusManagementService it exercises.
Flutter's build pipeline and SemanticsService.announce() operate asynchronously. Announcements triggered too early (before the semantic tree settles) may be swallowed silently on both platforms, causing acceptance criteria around the 500ms window to fail intermittently in CI and on device, which would block pilot launch.
Mitigation & Contingency
Mitigation: Implement the LiveRegionAnnouncer with a post-frame callback delay and an internal timing guard. Write integration tests using WidgetTester.pump() sequences that verify announcement delivery across multiple frame boundaries. Validate on physical devices at each sprint boundary, not only in CI.
Contingency: If consistent announcement timing cannot be achieved within Flutter's semantic pipeline, switch to a platform channel approach that calls native UIAccessibility.post (iOS) and AccessibilityManager.announce (Android) directly, bypassing Flutter's intermediary.
Flutter does not natively emit a focus-gain event to Dart code when VoiceOver or TalkBack moves focus to a specific widget. If the intercept mechanism for the SensitiveFieldWarningDialog relies on an unsupported or undocumented hook in the semantics tree, it may miss focus events for some field types or in some navigation contexts, leaving sensitive data unprotected.
Mitigation & Contingency
Mitigation: Prototype the focus-intercept mechanism during the first sprint of this epic, before building the dialog UI. Evaluate Flutter's SemanticsBinding.instance callbacks and custom SemanticsActions as intercept points. Document the chosen mechanism with platform compatibility notes.
Contingency: If no reliable focus-intercept is available, implement an alternative where sensitive fields show a static 'Screen reader active — tap to reveal' overlay instead of an OS dialog, which is less seamless but achieves equivalent privacy protection without relying on an unreliable event hook.
The AccessibilityTestHarness depends on internal flutter_test semantic tree APIs that can change between Flutter minor versions. If the project upgrades Flutter during this epic, the harness may break silently, causing CI accessibility tests to pass while actually skipping assertions.
Mitigation & Contingency
Mitigation: Pin the Flutter SDK version in pubspec.yaml for the duration of this epic. Document which flutter_test APIs are used and their stability tier. Add a canary test that explicitly fails if the semantic tree API surface changes.
Contingency: If a forced Flutter upgrade breaks the harness, prioritise patching the harness as a blocking task before any other epic work continues, using the canary test failure as the trigger.