Unit test ReminderEvaluationService
epic-assignment-follow-up-reminders-services-task-004 — Write comprehensive unit tests for ReminderEvaluationService covering: result is none when days are below remind threshold, result is remind when days meet or exceed remind threshold, result is escalate when days meet or exceed escalate threshold, no-contact-ever edge case returns escalate, and threshold boundary conditions. Mock all injectable dependencies.
Acceptance Criteria
Technical Requirements
Execution Context
Tier 2 - 518 tasks
Can start after Tier 1 completes
Implementation Notes
Inject a `clockFn` (`DateTime Function()`) into `ReminderEvaluationServiceImpl` to enable deterministic time in tests — set it to `() => DateTime.utc(2025, 6, 15)` in test setup. Use Mockito's `when().thenAnswer()` pattern to stub repository responses. For the no-contact-ever test, stub the repository to return `null` for `getLastContactDate(assignmentId)`. Write a shared `_makeThresholds({int remind = 7, int escalate = 14})` helper to reduce boilerplate across threshold tests.
Prefer manual fakes over generated mocks if the repository interface is simple — fewer dependencies and faster test compilation.
Testing Requirements
This task IS the testing requirement. Structure tests using `group()` blocks per scenario category: (1) below-threshold group, (2) remind-threshold group, (3) escalate-threshold group, (4) no-contact-ever group, (5) boundary-condition group. Use `setUp()` to instantiate the service with injected mocks before each test. Parameterize boundary tests using a table-driven approach where possible.
Verify that exhaustive switch on `ReminderEvaluationResult` in test assertions catches compiler errors if new variants are added.
The idempotency window (how long after a reminder is sent before another can be sent for the same assignment) is not explicitly specified. An incorrect window — too short, duplicate reminders appear; too long, a resolved and re-opened situation is not re-notified. This ambiguity could result in user-visible bugs post-launch.
Mitigation & Contingency
Mitigation: Before implementation, define the idempotency window explicitly with stakeholders: a reminder is suppressed if a same-type notification record exists with sent_at within the last (reminder_days - 1) days. Document this rule as a named constant in the service with a comment referencing the decision.
Contingency: If the window is wrong in production, it is a single constant change with a hotfix deployment. The notification_log table allows re-processing without data migration.
For organisations with thousands of open assignments (e.g., NHF with 1,400 chapters), the daily scheduler query over all open assignments could time out or consume excessive Supabase compute units, especially if the contact tracking query lacks proper indexing.
Mitigation & Contingency
Mitigation: Add a composite index on assignments(status, last_contact_date) before running performance tests. Use cursor-based pagination in the scheduler (query 500 rows at a time). Run a load test with 10,000 synthetic assignments as described in the feature documentation before merging.
Contingency: If the query is too slow for synchronous execution, move the evaluation to the Edge Function (cron trigger epic) and use Supabase's built-in parallelism. The service interface does not change, only the execution context.
If the push notification service fails (FCM outage, invalid device token) during dispatch, the in-app notification may already be persisted but the push is silently lost. Inconsistent state makes it impossible to report accurate delivery status.
Mitigation & Contingency
Mitigation: Implement push dispatch and in-app persistence as separate operations with independent error handling. Record delivery_status as 'pending', 'delivered', or 'failed' on the notification_log row. Retry failed push deliveries up to 3 times with exponential backoff.
Contingency: If FCM is consistently unavailable, the in-app notification is still visible to the user, providing a degraded but functional fallback. Alert on consecutive push failures via the cron trigger's error logging.