docs: add code examples of openapi client usage

Author: skarzi

README.md

@@ -66,9 +66,10 @@ def test_response_documentation(client):
 If you are using the Django testing framework, you can create a base APITestCase that incorporates schema validation:
 
 ```python
-from openapi_tester.schema_tester import SchemaTester
-from rest_framework.test import APITestCase
 from rest_framework.response import Response
+from rest_framework.test import APITestCase
+
+from openapi_tester.schema_tester import SchemaTester
 
 schema_tester = SchemaTester()
 
@@ -200,8 +201,7 @@ If you wish to validate each response against OpenAPI schema when writing
 unit tests - `OpenAPIClient` is what you need!
 
 To use `OpenAPIClient` simply pass `SchemaTester` instance that should be used
-to validate responses and then use it like regular Django testing client
-(TIP: add custom fixture if you are using `pytest` to avoid code boilerplate):
+to validate responses and then use it like regular Django testing client:
 
 ```python
 schema_tester = SchemaTester()
@@ -210,9 +210,46 @@ response = client.get('/api/v1/tests/123/')
 ```
 
 To force all developers working on the project to use `OpenAPIClient` simply
-override the `client` fixture (when using `pytest-django`) or provide custom
-test cases implementation (when using standard Django `unitest`-based approach)
-and then you will be sure all newly implemented views will be validated against
+override the `client` fixture (when using `pytest` with `pytest-django`):
+
+```python
+from pytest_django.lazy_django import skip_if_no_django
+
+from openapi_tester.schema_tester import SchemaTester
+
+
+@pytest.fixture
+def schema_tester():
+    return SchemaTester()
+
+
+@pytest.fixture
+def client(schema_tester):
+    skip_if_no_django()
+
+    from openapi_tester.clients import OpenAPIClient
+
+    return OpenAPIClient(schema_tester=schema_tester)
+```
+
+If you are using plain Django test framework, we suggest to create custom
+test case implementation:
+
+```python
+import functools
+
+from django.test.testcases import SimpleTestCase
+from openapi_tester.clients import OpenAPIClient
+from openapi_tester.schema_tester import SchemaTester
+
+schema_tester = SchemaTester()
+
+
+class MyTestCase(SimpleTestCase):
+    client_class = functools.partial(OpenAPIClient, schema_tester=schema_tester)
+```
+
+This will ensure you all newly implemented views will be validated against
 the OpenAPI schema.
 
 ## Known Issues

tests/test_clients.py

@@ -1,6 +1,8 @@
+import functools
 import json
 
 import pytest
+from django.test.testcases import SimpleTestCase
 from rest_framework import status
 
 from openapi_tester.clients import OpenAPIClient
@@ -73,3 +75,20 @@ def test_request_invalid_response(
     """Ensure ``SchemaTester`` raises an exception when response is invalid."""
     with pytest.raises(**raises_kwargs):  # noqa: PT010
         openapi_client.generic(**generic_kwargs)
+
+
+def test_django_testcase_client_class():
+    """Ensure example from README.md about Django test case works fine."""
+
+    class DummyTestCase(SimpleTestCase):
+        """Django ``TestCase`` with ``OpenAPIClient`` client."""
+
+        client_class = functools.partial(
+            OpenAPIClient,
+            schema_tester=SchemaTester(),
+        )
+
+    test_case = DummyTestCase()
+    test_case._pre_setup()
+
+    assert isinstance(test_case.client, OpenAPIClient)