diff --git a/graphene_django/tests/test_utils.py b/graphene_django/tests/test_utils.py
index c0d376b..24f142e 100644
--- a/graphene_django/tests/test_utils.py
+++ b/graphene_django/tests/test_utils.py
@@ -40,7 +40,7 @@ def test_camelize():
 @patch("graphene_django.utils.testing.Client.post")
 def test_graphql_test_case_op_name(post_mock):
     """
-    Test that `GraphQLTestCase.query()`'s `op_name` argument produces an `operationName` field.
+    Test that `GraphQLTestCase.query()`'s `operation_name` argument produces an `operationName` field.
     """
 
     class TestClass(GraphQLTestCase):
@@ -51,7 +51,7 @@ def test_graphql_test_case_op_name(post_mock):
 
     tc = TestClass()
     tc.setUpClass()
-    tc.query("query { }", op_name="QueryName")
+    tc.query("query { }", operation_name="QueryName")
     body = json.loads(post_mock.call_args.args[1])
     # `operationName` field from https://graphql.org/learn/serving-over-http/#post-request
     assert (
diff --git a/graphene_django/utils/testing.py b/graphene_django/utils/testing.py
index 0f68a51..0260e13 100644
--- a/graphene_django/utils/testing.py
+++ b/graphene_django/utils/testing.py
@@ -24,11 +24,13 @@ class GraphQLTestCase(TestCase):
 
         cls._client = Client()
 
-    def query(self, query, op_name=None, input_data=None, variables=None, headers=None):
+    def query(
+        self, query, operation_name=None, input_data=None, variables=None, headers=None
+    ):
         """
         Args:
             query (string)    - GraphQL query to run
-            op_name (string)  - If the query is a mutation or named query, you must
+            operation_name (string)  - If the query is a mutation or named query, you must
                                 supply the op_name.  For annon queries ("{ ... }"),
                                 should be None (default).
             input_data (dict) - If provided, the $input variable in GraphQL will be set
@@ -44,8 +46,8 @@ class GraphQLTestCase(TestCase):
             Response object from client
         """
         body = {"query": query}
-        if op_name:
-            body["operationName"] = op_name
+        if operation_name:
+            body["operationName"] = operation_name
         if variables:
             body["variables"] = variables
         if input_data: