m12-pr16: partition rotation health invariants (tests/db/test_partition_health.py)

[BalaShankar9]

m12-pr16: partition rotation health invariants (tests/db/test_partition_health.py)

Adds 15 unit tests pinning health invariants for the events_outbox
partition rotation introduced in m7-pr27a (ADR-0037). Complements the
existing tests/integration/test_outbox_partitions.py (migration regex

• opt-in live-DB) by covering gaps that integration test does not:

Time-math (5 tests, pure helper mirroring SQL date_trunc + i months)

• YYYY_MM zero-pad
• current month + N (count = N+1)
• year roll at December
• 25-month span at max lookahead, monotonic, no dups
• day-of-month invariance

Cross-file contract (8 tests against migration / runbook / ADR)

• bootstrap and cron use identical months_ahead (=4)
• p_months_ahead bounds 0..24 RAISE present
• EXCEPTION WHEN OTHERS still inserts audit row with err_msg
• audit columns pinned (table_name text, ran_at timestamptz, etc.)
• cron command body is bare function call (no error-swallowing wrapper)
• daily 00:01 UTC schedule literal
• runbook 36h alert window contract (24h cadence + 12h grace)
• ADR-0037 status remains Accepted
• SAFETY header references ADR-0037

Sanity (1 test): helper count vs constant.

Why "health" vs existing rotation tests: the migration tests pin
WHAT was deployed; these pin the INVARIANTS the daily job and alert
depend on. If someone changes cron to twice-daily but forgets to
update the runbook alert window, or renames an audit column the
Prometheus query reads, that drift now fails CI.

Files

• backend/tests/db/init.py (new, empty)
• backend/tests/db/test_partition_health.py (new, 15 tests)
• context/TESTING_CONTEXT.md (moved from Planned to Shipped m12-pr16)
• context/CHANGELOG_INTELLIGENCE.md (m12-pr16 row)

Validation

• pytest tests/db/test_partition_health.py -v -> 15 passed in 0.03s
• No other tests touched; no production code touched.

Stacked on PR #33 (m12-pr15). Base branch: m12-pr15-test-dlq.

[Copilot]

Pull request overview

Adds a new “health invariants” unit test suite that statically pins the cross-file contract for events_outbox partition rotation (migration ↔ cron schedule ↔ runbook ↔ ADR), complementing the existing integration coverage.

Changes:

• Added 15 unit tests (backend/tests/db/test_partition_health.py) that verify time-math invariants and contract invariants across the rotation migration, runbook, and ADR.
• Added backend/tests/db/__init__.py to establish the tests/db package.
• Updated context docs to mark this test suite as shipped and to add the m12-pr16 changelog ledger row.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
context/TESTING_CONTEXT.md	Moves the partition health tests entry from “Planned” to “Shipped (m12-pr16)”.
context/CHANGELOG_INTELLIGENCE.md	Adds the m12-pr16 ledger row and links m12-pr15 to PR #33.
backend/tests/db/test_partition_health.py	New unit tests that pin partition rotation invariants across migration/runbook/ADR plus pure time-math helper checks.
backend/tests/db/init.py	New (empty) package marker for backend/tests/db.

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