test : add unit tests for WorkflowScheduler._should_run datetime logic

[tmdeveloper007]

Summary of What Needs to be Done:

Add unit tests for WorkflowScheduler._should_run in backend/secuscan/workflows.py. This method is a pure datetime-comparison function that determines whether a scheduled workflow should run based on the elapsed time since its last execution. It currently has no test coverage.

The method handles three cases:

1. last_run_at is None (never run) → return True
2. last_run_at is a naive datetime (SQLite returns no timezone suffix) → treat as UTC
3. last_run_at is an aware datetime → compare with current UTC time
4. elapsed >= schedule_seconds → return True, else False

Changes that Need to be Made:

Create testing/backend/unit/test_workflows_scheduler_should_run.py with the following test cases:

• test_no_last_run_at_returns_true: when last_run_at=None, _should_run returns True regardless of schedule_seconds
• test_elapsed_exceeds_schedule_returns_true: when enough time has passed, returns True
• test_elapsed_less_than_schedule_returns_false: when not enough time has passed, returns False
• test_naive_datetime_treated_as_utc: SQLite datetime format (no Z, no +00:00) is treated as UTC — a naive datetime 30s ago with schedule_seconds=60 should return False
• test_aware_datetime_comparison_correct: an aware datetime 120s ago with schedule_seconds=60 returns True
• test_zero_schedule_seconds: schedule_seconds=0 always returns True
• test_exactly_at_boundary: elapsed == schedule_seconds returns True

Import the real WorkflowScheduler from backend.secuscan.workflows. Instantiate it directly (WorkflowScheduler()) — the _should_run method does not require a running scheduler or database.

Impact that it would Provide:

• Reliability: ensures the scheduler respects timing constraints correctly
• Regression safety: prevents silent scheduler overruns if datetime handling changes
• Documentation: the test cases document the expected behavior for naive vs aware datetimes

Note: This task is being handled by tmdeveloper007 — please assign to that account when picking it up.

[tmdeveloper007]

Closing this issue — the WorkflowScheduler._should_run method is already comprehensively tested in testing/backend/unit/test_workflows_scheduler.py (which covers None handling, elapsed boundaries, naive datetime handling, and Z/+00:00 suffixes). No additional test file is needed.