Write Unit Tests for Way Forward Task Service

Before writing tests, confirm WayForwardTaskService exposes its dependencies (repository, task queue, clock) via constructor injection — if not, refactor before writing tests. For the rollback test, if Dart lacks built-in transaction scope, simulate rollback via a collected list: service accumulates created tasks in a local list and only calls repository.insertBatch() after all items are validated — test this by verifying insertBatch is called once with all items or not at all. The idempotency test should assert the exact WayForwardTaskCreationResult.alreadyExisted variant is returned (use expect with isA() or pattern matching on sealed class). Define a buildReport({String?

coordinatorId, List items}) factory in test/helpers/ to reduce boilerplate across tests.

Pure unit tests with flutter_test and mockito. Mock IWayForwardItemRepository and ITaskQueue using @GenerateMocks. For rollback test, use when().thenThrow() on the repository mock for the second invocation using mockito's answer sequencing (thenAnswer chained calls). Verify task queue signal count with verify(mockQueue.signal(any)).called(N).

Due date calculation tests should be extracted into a separate group() block that tests the pure calculation function directly if it is extracted. Use fake DateTime via a Clock abstraction — do not rely on DateTime.now() in tests. Run flutter test --coverage to confirm ≥ 90% line coverage.