allow shift registrations end to start

shiftregister/app/models.py

@@ -145,10 +145,10 @@ class Helper(models.Model):
                 )
                 |
                 # Case 2: End time falls between new shift's start and end
-                Q(shift_end__gt=shift.start_at, shift_end__lte=new_shift_end)
+                Q(shift_end__gt=shift.start_at, shift_end__lt=new_shift_end)
                 |
                 # Case 3: Completely encompasses the new shift
-                Q(shift__start_at__lte=shift.start_at, shift_end__gte=new_shift_end)
+                Q(shift__start_at__lt=shift.start_at, shift_end__gt=new_shift_end)
             )
             .first()
         )

shiftregister/app/tests.py

@@ -43,11 +43,32 @@ class ShiftOverlapTests(TestCase):
         )
         self.assertIsNone(self.helper.has_overlapping_shift(shift_before))
 
+    def test_back_to_back_shifts(self):
+        """Test that a shift starting exactly when another ends is allowed"""
+        shift_after = Shift.objects.create(
+            room=self.room,
+            start_at=self.base_shift.start_at + self.base_shift.duration,
+            duration=timedelta(hours=1),
+            required_helpers=1,
+        )
+        self.assertIsNone(self.helper.has_overlapping_shift(shift_after))
+
+        # Also test the reverse case - registering for a shift that ends exactly when another begins
+        self.base_registration.delete()
+        ShiftRegistration.objects.create(
+            shift=shift_after,
+            helper=self.helper,
+            state=ShiftRegistration.RegState.REGISTERED,
+        )
+        self.assertIsNone(self.helper.has_overlapping_shift(self.base_shift))
+
     def test_no_overlap_after(self):
         """Test a shift that starts after the base shift ends"""
         shift_after = Shift.objects.create(
             room=self.room,
-            start_at=self.base_shift.start_at + timedelta(hours=4),
+            start_at=self.base_shift.start_at
+            + self.base_shift.duration
+            + timedelta(hours=1),
             duration=timedelta(hours=1),
             required_helpers=1,
         )