Pure-function invariants that example tests can't express at scale:
- Weather.round_to_iemre_grid/2, HrrrClient.nearest_hrrr_hour/1,
NexradClient.round_to_5min/1, NarrClient.snap_to_analysis_hour/1:
each is idempotent, its output satisfies a grid/slot-membership
predicate, and lies within a bounded distance of the input.
- NarrClient.in_coverage?/1: coverage_end is an exclusive upper
bound; any timestamp after it is out of coverage.
- IemreFetchWorker.backoff/1: result is in [120, 21_600], monotonic
non-decreasing in attempt, equals 120*2^(attempt-1) pre-cap.
- Contact submission_changeset notes field: every non-blank string
up to 2000 chars validates; any longer string is rejected.
22 new properties (139 → 161 including existing); all 2,300 tests
green, credo clean.
