Write accessibility tests for wizard, nav, and modal components
epic-screen-reader-support-complex-widgets-task-017 — Write flutter_test accessibility tests covering all three high-complexity UI components: ActivityWizardStepSemantics (step announcements, focus placement, inline error reading), AccessibleBottomNavigation (label correctness, selected-state semantics, tab-switch announcements), and AccessibleModalSheet (focus trapping, trigger focus restoration, dialog role announcement). Use Flutter's SemanticsController and AccessibilityGuideline matchers.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 3 - 413 tasks
Can start after Tier 2 completes
Implementation Notes
The highest-risk area is the focus-trapping test for AccessibleModalSheet — Flutter's semantics tree does not natively enforce focus trapping in tests the way a browser does. The recommended approach is to collect all SemanticsNode IDs reachable via repeated SemanticsAction.moveFocusForward from within the modal and assert the set never contains a node whose ancestor is outside the modal's overlay entry. For liveRegion / announcement verification, Flutter's SemanticsController.announce is the correct API — but in tests you may need to spy on it by wrapping the SemanticsBinding. Use a TestWidgetsFlutterBinding.ensureInitialized() override with a custom SemanticsBinding to capture announcements.
For the ActivityWizard step announcement test, ensure the wizard step model is injectable (pass steps as a constructor parameter) so tests can drive step transitions without touching real activity data. The AccessibleBottomNavigation tests should use the real widget (not a mock) to catch regressions in the actual Semantics node setup — use a minimal Scaffold + BottomNavigation fixture rather than the full app.
Testing Requirements
Use flutter_test exclusively (not flutter_driver or integration_test package) to keep tests fast and headless. Enable semantics globally in each test with tester.ensureSemantics() and dispose the returned handle in tearDown. Use tester.getSemantics(find.byType(X)) to retrieve SemanticsData for assertion. For announcement tests, use a SemanticsController mock that records SemanticsAction.announce calls and verify the recorded announcements list.
For focus trapping tests, iterate through all reachable semantics nodes while the modal is open and assert that none are outside the modal's subtree. For tab-switch tests, programmatically call setState or tap the BottomNavItem and then assert SemanticsFlag.isSelected via tester.getSemantics(). Structure tests in three files: activity_wizard_semantics_test.dart, accessible_bottom_nav_test.dart, accessible_modal_sheet_test.dart. Share a common AccessibilityTestFixtures class for repeated widget pump setups.
All three files must carry the flutter_test tag 'accessibility_components' for selective CI execution.
Flutter does not natively enforce a focus trap within a bottom sheet or modal dialog in the semantic tree — VoiceOver and TalkBack can navigate outside the sheet to background content. Implementing a reliable focus trap requires overriding the semantic tree, which may conflict with the existing modal helper infrastructure in the app and require changes to shared components beyond this feature's scope.
Mitigation & Contingency
Mitigation: Prototype the focus trap on the first modal sheet implementation before building the remaining sheets. Evaluate Flutter's ExcludeSemantics and BlockSemantics widgets as the trap mechanism, and coordinate with the team owning the shared modal helpers to agree on a non-breaking integration point before writing production code.
Contingency: If a complete semantic focus trap cannot be implemented without breaking existing modal patterns, implement a partial solution using FocusScope with autofocus on the modal's first element and a prominent 'Return to main content' semantic action, documenting the deviation from WCAG 2.4.3 with a scheduled remediation item.
The activity wizard uses BLoC state management and the UI rebuilds the entire step widget subtree on transition. If the semantic tree is traversed by VoiceOver before the build cycle settles, focus may land on a stale or partially rendered step, causing the wrong step label or progress value to be announced. This is particularly problematic for blind users who cannot visually verify the announcement against the screen.
Mitigation & Contingency
Mitigation: Coordinate ActivityWizardStepSemantics with FocusManagementService (from the core services epic) to delay focus placement until the post-build callback confirms the new step's semantic tree is complete. Write integration tests using the AccessibilityTestHarness that assert the full announcement sequence across all five wizard steps.
Contingency: If post-build focus delay is insufficient due to async BLoC emission timing, add an explicit semantic notification barrier in the wizard cubit that emits a 'step ready' event only after the new widget tree has been marked as built, decoupling the announcement trigger from the raw state transition.
Automated WCAG contrast ratio checking on widget tree snapshots may produce false positives for gradient backgrounds, dark-mode overrides, or design token overrides that are resolved at runtime but appear as unresolvable colours at static analysis time. Excessive false positives would erode team trust in the CI gate, leading to suppression rules that also mask real violations.
Mitigation & Contingency
Mitigation: Scope the WCAGComplianceChecker to check only solid-colour backgrounds in the first iteration, explicitly excluding gradients from contrast checks with documented rationale. Design the check output to distinguish 'undetermined' (gradient/unknown) from 'fail' (solid colour below threshold) so the team can take targeted action on genuine failures only.
Contingency: If false positive rates exceed 20% of reported violations during initial CI runs, switch the CI gate from a hard build failure to a warning annotation on the pull request, combined with a mandatory manual review step, until the checker's rule set has been tuned to match actual design token values.