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testland/timezone-test-matrix-builder
Use when a codebase needs time zone, DST and leap-year test coverage derived from its own date and time code. Finds where times are stored, computed, displayed, scheduled or billed, picks the edge cases that matter and writes test stubs using the language's fake-clock library.
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test-catalog.mdreferences/
Per-category test catalog
The test cases each touchpoint category should exercise. Pick the rows matching the category assigned during inventory (Step 1).
Storage tests
| Test | Pattern |
|---|---|
| Round-trip RFC 3339 | parse → emit → parse → assert equal |
| Round-trip via JSON | serialise object → deserialise → assert |
| Microsecond precision preserved | .123456Z survives DB store/load |
| Zone information preserved or normalized to UTC | Document the policy |
Business-logic tests
| Test | Pattern |
|---|---|
| DST spring-forward | Schedule at 02:30 local on transition day; verify behaviour |
| DST fall-back | Same 01:30 local appearing twice; verify ordering |
| Leap day Feb 29 | "1 year from Feb 29 2024" → Feb 28 2025 (Per ICU) |
| Year-end rollover | "Tomorrow" on Dec 31 |
| Month-end | Jan 31 + 1 month = Feb 28 / 29 (per library) |
| Negative durations | Operations on "5 minutes ago" |
| Leap second tolerance | Code uses monotonic time per dst-transition-reference references/leap-seconds.md |
Cron tests
| Test | Pattern |
|---|---|
| Daily 02:30 EST cron on spring-forward | Doesn't fire OR fires at 03:30 (per cron spec) |
| Daily 01:30 EST cron on fall-back | Fires once vs twice (per spec) |
| Monthly on Feb 29 (non-leap year) | Fires on Feb 28 OR not at all |
| Weekly cron crossing DST | 1-hour offset for one week |
Billing tests
| Test | Pattern |
|---|---|
| Billing on month-end across leap year | Feb 28 vs Feb 29 handling |
| Billing window across DST | Hour gain / loss in the period |
| Pro-ration calculation | Across DST boundary |
| Multi-tenant timezone variance | Same wall-clock hour ≠ same UTC |
Display tests
| Test | Pattern |
|---|---|
| Per-user TZ formatting | User in Asia/Tokyo sees 09:00 JST; user in Europe/London sees 00:00 GMT |
| ISO 8601 vs human-readable | Localised display ≠ wire format |
| 24h vs 12h convention | Per user locale |
| Relative time ("2 hours ago") | Per system locale |