| 1 | package calendartest |
| 2 | |
| 3 | import ( |
| 4 | "testing" |
| 5 | "time" |
| 6 | |
| 7 | calendar "amadan.net/oficina/calendar/internal/calendar" |
| 8 | ) |
| 9 | |
| 10 | // The two hours a year that break calendars, pinned against |
| 11 | // Europe/Dublin 2026 — DST starts 29 March and ends 25 October, both at |
| 12 | // 01:00 UTC. |
| 13 | // |
| 14 | // There is no correct answer here and Go does not promise one, so this |
| 15 | // test does not assert correctness. It asserts THE ANSWER, so that a Go |
| 16 | // upgrade or a tzdata bump that changes it fails loudly here rather |
| 17 | // than moving somebody's meeting quietly. |
| 18 | // |
| 19 | // The two cases resolve differently and that is the point of testing |
| 20 | // both: the gap takes the pre-transition offset, the fold takes the |
| 21 | // post-transition one. |
| 22 | func TestDSTGapAndFold(t *testing.T) { |
| 23 | const dublin = "Europe/Dublin" |
| 24 | |
| 25 | t.Run("the gap moves forward", func(t *testing.T) { |
| 26 | // Local 01:00 jumps to 02:00, so 01:30 never happens. |
| 27 | got, err := calendar.ToUTC("2026-03-29T01:30", dublin, false) |
| 28 | if err != nil { |
| 29 | t.Fatalf("ToUTC: %v", err) |
| 30 | } |
| 31 | if want := int64(1774747800); got != want { |
| 32 | t.Errorf("gap 01:30: unix = %d, want %d", got, want) |
| 33 | } |
| 34 | // Reading it back must land AFTER the written time, never |
| 35 | // before: an event in the gap that moved backwards would |
| 36 | // happen before the person expected it. |
| 37 | back, err := calendar.InZone(got, dublin) |
| 38 | if err != nil { |
| 39 | t.Fatalf("InZone: %v", err) |
| 40 | } |
| 41 | if h, m := back.Hour(), back.Minute(); h != 2 || m != 30 { |
| 42 | t.Errorf("gap 01:30 reads back as %02d:%02d, want 02:30", h, m) |
| 43 | } |
| 44 | }) |
| 45 | |
| 46 | t.Run("the fold takes the second occurrence", func(t *testing.T) { |
| 47 | // Local 02:00 falls back to 01:00, so 01:30 happens twice: |
| 48 | // once at 00:30 UTC (offset +1) and once at 01:30 UTC |
| 49 | // (offset 0). Go returns the second. |
| 50 | got, err := calendar.ToUTC("2026-10-25T01:30", dublin, false) |
| 51 | if err != nil { |
| 52 | t.Fatalf("ToUTC: %v", err) |
| 53 | } |
| 54 | if want := int64(1792891800); got != want { |
| 55 | t.Errorf("fold 01:30: unix = %d, want %d (the second occurrence)", got, want) |
| 56 | } |
| 57 | }) |
| 58 | } |
| 59 | |
| 60 | // A day is not always 24 hours long. On the two DST nights it is 23 or |
| 61 | // 25, and a day view that added a fixed duration would run an hour into |
| 62 | // the next day or stop an hour short of the end of this one. |
| 63 | func TestDayBoundsFollowDSTRatherThanTwentyFourHours(t *testing.T) { |
| 64 | const dublin = "Europe/Dublin" |
| 65 | for _, tc := range []struct { |
| 66 | name string |
| 67 | day time.Time |
| 68 | hours float64 |
| 69 | }{ |
| 70 | {"an ordinary day is 24 hours", time.Date(2026, 6, 1, 12, 0, 0, 0, time.UTC), 24}, |
| 71 | {"the spring-forward day is 23", time.Date(2026, 3, 29, 12, 0, 0, 0, time.UTC), 23}, |
| 72 | {"the fall-back day is 25", time.Date(2026, 10, 25, 12, 0, 0, 0, time.UTC), 25}, |
| 73 | } { |
| 74 | t.Run(tc.name, func(t *testing.T) { |
| 75 | start, end, err := calendar.DayBounds(tc.day, dublin) |
| 76 | if err != nil { |
| 77 | t.Fatalf("DayBounds: %v", err) |
| 78 | } |
| 79 | if got := float64(end-start) / 3600; got != tc.hours { |
| 80 | t.Errorf("day length = %v hours, want %v", got, tc.hours) |
| 81 | } |
| 82 | }) |
| 83 | } |
| 84 | } |
| 85 | |
| 86 | // An all-day event is a date, not an instant. Storing it as a timed |
| 87 | // event at midnight UTC is the bug that shows a birthday on the wrong |
| 88 | // day for everybody west of Greenwich. |
| 89 | func TestAllDayIsMidnightInItsOwnZone(t *testing.T) { |
| 90 | dublin, err := calendar.ToUTC("2026-09-02", "Europe/Dublin", true) |
| 91 | if err != nil { |
| 92 | t.Fatalf("ToUTC Dublin: %v", err) |
| 93 | } |
| 94 | tokyo, err := calendar.ToUTC("2026-09-02", "Asia/Tokyo", true) |
| 95 | if err != nil { |
| 96 | t.Fatalf("ToUTC Tokyo: %v", err) |
| 97 | } |
| 98 | if dublin == tokyo { |
| 99 | t.Error("the same date in two zones produced the same instant; all-day is being stored as UTC midnight") |
| 100 | } |
| 101 | // Tokyo is ahead, so its midnight comes first. |
| 102 | if tokyo >= dublin { |
| 103 | t.Errorf("Tokyo midnight (%d) should precede Dublin midnight (%d)", tokyo, dublin) |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | // An empty zone is UTC, never the server's local zone — which is an |
| 108 | // accident of provisioning and would shift every unzoned event's day |
| 109 | // boundaries the first time the fleet moved region. |
| 110 | func TestEmptyZoneIsUTCNotTheServers(t *testing.T) { |
| 111 | empty, err := calendar.ToUTC("2026-09-02T09:00", "", false) |
| 112 | if err != nil { |
| 113 | t.Fatalf("ToUTC: %v", err) |
| 114 | } |
| 115 | utc, err := calendar.ToUTC("2026-09-02T09:00", "UTC", false) |
| 116 | if err != nil { |
| 117 | t.Fatalf("ToUTC: %v", err) |
| 118 | } |
| 119 | if empty != utc { |
| 120 | t.Errorf("empty zone = %d, UTC = %d; they must agree", empty, utc) |
| 121 | } |
| 122 | } |
| 123 | |
| 124 | func TestUnknownZoneIsRefused(t *testing.T) { |
| 125 | if _, err := calendar.ToUTC("2026-09-02T09:00", "Mars/Olympus_Mons", false); err == nil { |
| 126 | t.Error("an unknown zone was accepted") |
| 127 | } |
| 128 | } |
| 129 | |
amadan