Add unit test (#8550)

- Unit test to ensure event is fired when stock item is created OR updated
- Ref: https://github.com/inventree/InvenTree/pull/8546
- Ref: https://github.com/inventree/InvenTree/issues/8452

src/backend/InvenTree/stock/tests.py

@@ -951,6 +951,45 @@ class StockTest(StockTestBase):
         # Final purchase price should be the weighted average
         self.assertAlmostEqual(s1.purchase_price.amount, 16.875, places=3)
 
+    def test_notify_low_stock(self):
+        """Test that the 'notify_low_stock' task is triggered correctly."""
+        FUNC_NAME = 'part.tasks.notify_low_stock_if_required'
+
+        from django_q.models import OrmQ
+
+        # Start from a blank slate
+        OrmQ.objects.all().delete()
+
+        def check_func() -> bool:
+            """Check that the 'notify_low_stock_if_required' task has been triggered."""
+            found = False
+            for task in OrmQ.objects.all():
+                if task.func() == FUNC_NAME:
+                    found = True
+                    break
+
+            # Clear the task queue (for the next test)
+            OrmQ.objects.all().delete()
+
+            return found
+
+        self.assertFalse(check_func())
+
+        part = Part.objects.first()
+
+        # Create a new stock item for this part
+        item = StockItem.objects.create(
+            part=part, quantity=100, location=StockLocation.objects.first()
+        )
+
+        self.assertTrue(check_func())
+        self.assertFalse(check_func())
+
+        # Re-count the stock item
+        item.stocktake(99, None)
+
+        self.assertTrue(check_func())
+
 
 class StockBarcodeTest(StockTestBase):
     """Run barcode tests for the stock app."""