test: standalone SI creates and attaches serial nos
diff --git a/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py b/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
index 6d929e4..271e02a 100644
--- a/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
+++ b/erpnext/accounts/doctype/sales_invoice/test_sales_invoice.py
@@ -2615,6 +2615,14 @@
 
 		frappe.db.set_value('Accounts Settings', None, 'acc_frozen_upto', None)
 
+	def test_standalone_serial_no_return(self):
+		si = create_sales_invoice(item_code="_Test Serialized Item With Series", update_stock=True, is_return=True, qty=-1)
+		si.submit()
+		self.assertTrue(si.items[0].serial_no)
+
+		return si
+
+
 def get_sales_invoice_for_e_invoice():
 	si = make_sales_invoice_for_ewaybill()
 	si.naming_series = 'INV-2020-.#####'