Fix next_occurrence function

data_safe_haven/functions/strings.py

@@ -46,8 +46,14 @@ def next_occurrence(
             minute=minute,
             second=0,
             microsecond=0,
-        ) + datetime.timedelta(days=1)
+        )
         utc_dt = local_dt.astimezone(pytz.utc)
+        # Add one day until this datetime is at least 1 hour in the future.
+        # This ensures that any Azure functions which depend on this datetime being in
+        # the future should treat it as valid.
+        utc_near_future = datetime.datetime.now(pytz.utc) + datetime.timedelta(hours=1)
+        while utc_dt < utc_near_future:
+            utc_dt += datetime.timedelta(days=1)
         if time_format == "iso":
             return utc_dt.isoformat()
         elif time_format == "iso_minute":

tests/functions/test_strings.py

@@ -8,12 +8,25 @@
 from data_safe_haven.functions import next_occurrence, sanitise_sre_name
 
 
-def test_next_occurrence_is_within_next_day():
+def test_next_occurrence_will_occur_soon():
+    dt_utc_now = datetime.datetime.now(datetime.UTC)
     next_time = next_occurrence(5, 13, "Australia/Perth")
+    dt_utc_tomorrow = dt_utc_now + datetime.timedelta(days=1, hours=2)
     dt_next_time = datetime.datetime.fromisoformat(next_time)
+    assert dt_next_time > dt_utc_now
+    assert dt_next_time < dt_utc_tomorrow
+
+
+def test_next_occurrence_day_shift():
     dt_utc_now = datetime.datetime.now(datetime.UTC)
+    dt_perth_now = dt_utc_now.astimezone(pytz.timezone("Australia/Perth"))
+    next_time = next_occurrence(
+        dt_perth_now.hour, dt_perth_now.minute, "Australia/Perth"
+    )
+    dt_utc_tomorrow = dt_utc_now + datetime.timedelta(days=1, hours=2)
+    dt_next_time = datetime.datetime.fromisoformat(next_time)
     assert dt_next_time > dt_utc_now
-    assert dt_next_time < dt_utc_now + datetime.timedelta(days=1)
+    assert dt_next_time < dt_utc_tomorrow
 
 
 def test_next_occurrence_has_correct_time():