Unit-test accessibility service label correctness

Instantiate ExpenseTypeAccessibilityService with a controlled clock (inject a DateTime provider or use FakeAsync.run). Avoid any dependency on Flutter widget rendering — this is a pure Dart service test; no pumpWidget calls needed. Use a StreamController or simple callback list as the announcement sink so you can assert emissions without real platform channels. Parameterise the state-label test using a data-driven table (List of tuples) so adding new ExpenseType variants automatically expands coverage.

For the placeholder check, define the regex once as a top-level const and reuse it across all label assertions to keep the test DRY.

Use flutter_test with fake_async (via flutter_test's FakeAsync) to simulate time progression for debounce tests. Write example-based tests for each ExpenseType variant × state combination. Add a regex-based assertion that scans every returned label for common placeholder patterns (e.g. /\{\{.*?\}\}/, /%[sd]/, /<.*?>/).

Test the focus-order sort with a shuffled input list and assert the returned order matches expected priority. For debounce, schedule two rapid calls at t=0 and t=100 ms, advance fake clock to t=200 ms, and assert only one emission. Then schedule two calls at t=0 and t=200 ms and assert two emissions. Aim for 100% branch coverage of the service's public API.