Add a timezone test

Author: rkdarst

tests/test_calendar.py

@@ -1,3 +1,4 @@
+import datetime
 import io
 import textwrap
 
@@ -28,3 +29,39 @@ def test_calendar_event():
     assert cal_str.startswith('BEGIN:VCALENDAR')
     assert 'SUMMARY:Earth Day' in cal_str
     assert cal_str.endswith('END:VCALENDAR')
+
+def test_calendar_default_timezone():
+    cal = files_to_calendar(
+        [io.StringIO(textwrap.dedent(
+            '''
+            meta:
+              tz: Europe/Helsinki
+
+            events:
+              - summary: New year's day
+                begin: 2022-01-01 00:00:00
+                duration: {hours: 1}
+
+              - summary: February 1
+                begin: 2022-02-01 00:00:00 +02:00
+                duration: {hours: 1}
+            '''
+        ))]
+    )
+    cal_str = cal.serialize()
+    assert cal_str.startswith('BEGIN:VCALENDAR')
+    assert 'SUMMARY:New year' in cal_str
+    # It is possible that the ics-py TZID string changes, but hopefully this
+    # substring is fairly safe to test against.
+    assert 'Europe/Helsinki:20220101T000000' in cal_str
+    # Second event: explicit UTC offset specified.
+    assert '"UTC+02:00":20220201T000000' in cal_str
+    assert cal_str.endswith('END:VCALENDAR')
+
+    # Test again by normalizing to UTC.  Helsinki is two hours ahead, so the
+    # times should be 22:00:00.
+    cal.normalize(datetime.timezone.utc)
+    cal_norm_str = cal.serialize()
+    # 1 Feb midnight
+    assert 'DTSTART:20211231T220000Z' # 1 jan
+    assert 'DTSTART:20220131T220000Z' # 1 feb