Fix stocktake bug for counting serialized items (#12280)

* Fix stocktake bug for counting serialized items

* Add unit test

src/backend/InvenTree/stock/models.py

@@ -2706,8 +2706,8 @@ class StockItem(
             )
             tracking_info['old_status_logical'] = old_status_logical
 
-        if self.updateQuantity(count):
+        if self.serialized or self.updateQuantity(count):
-            tracking_info['quantity'] = float(count)
+            tracking_info['quantity'] = 1 if self.serialized else float(count)
 
             self.stocktake_date = InvenTree.helpers.current_date()
             self.stocktake_user = user
@@ -2731,7 +2731,7 @@ class StockItem(
                 StockEvents.ITEM_COUNTED,
                 'stockitem.counted',
                 id=self.id,
-            quantity=float(self.quantity),
+                quantity=1 if self.serialized else float(self.quantity),
             )
 
         return True

src/backend/InvenTree/stock/test_api.py

@@ -2289,6 +2289,32 @@ class StocktakeTest(StockAPITestCase):
             self.assertEqual(response.data['items'][0]['pk'], 1234)
             self.assertEqual(response.data['items'][0]['quantity'], target[endpoint])
 
+    def test_count_serialized(self):
+        """Test that counting a serialized stock item correctly updates stocktake_date."""
+        import datetime
+
+        # Fixture item pk=501 is a serialized item (serial=1)
+        item = StockItem.objects.get(pk=501)
+        self.assertTrue(item.serialized)
+        self.assertEqual(item.quantity, 1)
+
+        # Clear any existing stocktake date so we can verify it gets set
+        item.stocktake_date = None
+        item.save()
+
+        url = reverse('api-stock-count')
+
+        # Count the serialized item — quantity must be 1
+        data = {'items': [{'pk': item.pk, 'quantity': 1}]}
+        response = self.post(url, data, expected_code=201)
+
+        self.assertEqual(response.data['items'][0]['pk'], item.pk)
+        self.assertEqual(response.data['items'][0]['quantity'], '1.00000')
+
+        # stocktake_date must have been set to today
+        item.refresh_from_db()
+        self.assertEqual(item.stocktake_date, datetime.date.today())
+
     def test_transfer(self):
         """Test stock transfers."""
         stock_item = StockItem.objects.get(pk=1234)