Added GraphQLTransactionTestCase (#1099)

* Added GraphQLTransactionTestCase

- Adds support for testing code that is executed within a transaction

Reference: https://docs.djangoproject.com/en/3.1/topics/testing/tools/#django.test.TransactionTestCase
```
 For instance, you cannot test that a block of code is executing within a transaction, as is required when using select_for_update(). In those cases, you should use TransactionTestCase.
```

* Update testing.py

* Update testing.py

* Fixed formatting.

* Updated docs.

* Updated test.

* Update testing.rst

docs/testing.rst

@@ -82,6 +82,41 @@ Usage:
             # Add some more asserts if you like
             ...
 
+
+For testing mutations that are executed within a transaction you should subclass `GraphQLTransactionTestCase`
+
+Usage:
+
+.. code:: python
+
+    import json
+
+    from graphene_django.utils.testing import GraphQLTransactionTestCase
+
+    class MyFancyTransactionTestCase(GraphQLTransactionTestCase):
+
+        def test_some_mutation_that_executes_within_a_transaction(self):
+            response = self.query(
+                '''
+                mutation myMutation($input: MyMutationInput!) {
+                    myMutation(input: $input) {
+                        my-model {
+                            id
+                            name
+                        }
+                    }
+                }
+                ''',
+                op_name='myMutation',
+                input_data={'my_field': 'foo', 'other_field': 'bar'}
+            )
+
+            # This validates the status code and if you get errors
+            self.assertResponseNoErrors(response)
+
+            # Add some more asserts if you like
+            ...
+
 Using pytest
 ------------
 

graphene_django/tests/test_utils.py

@@ -83,6 +83,6 @@ def client_query(client):
 
 
 def test_pytest_fixture_usage(client_query):
-    response = graphql_query("query { test }")
+    response = client_query("query { test }")
     content = json.loads(response.content)
     assert content == {"data": {"test": "Hello World"}}

graphene_django/utils/testing.py

@@ -1,7 +1,7 @@
 import json
 import warnings
 
-from django.test import Client, TestCase
+from django.test import Client, TestCase, TransactionTestCase
 
 DEFAULT_GRAPHQL_URL = "/graphql/"
 
@@ -63,7 +63,7 @@ def graphql_query(
     return resp
 
 
-class GraphQLTestCase(TestCase):
+class GraphQLTestMixin(object):
     """
     Based on: https://www.sam.today/blog/testing-graphql-with-graphene-django/
     """
@@ -143,3 +143,11 @@ class GraphQLTestCase(TestCase):
         """
         content = json.loads(resp.content)
         self.assertIn("errors", list(content.keys()), msg or content)
+
+
+class GraphQLTestCase(GraphQLTestMixin, TestCase):
+    pass
+
+
+class GraphQLTransactionTestCase(GraphQLTestMixin, TransactionTestCase):
+    pass