Add documentation about how to transform factory request to DRF request

docs/api-guide/testing.md

@@ -102,6 +102,20 @@ This means that setting attributes directly on the request object may not always
     request.user = user
     response = view(request)
 
+In case you want to test the request having a REST famework's `Request` you have to transform it by-hand before:
+
+    class DummyView(APIView):
+        ...
+
+    factory = APIRequestFactory()
+    request = factory.get('/', {'demo': 'test'})
+    DRF_request = DummyView().initialize_request(request)
+    assert DRF_request.query_params == {'demo': ['test']}
+
+    request = factory.post('/', {'example': 'test'})
+    DRF_request = DummyView().initialize_request(request)
+    assert DRF_request.data.get('example') == 'test'
+
 ---
 
 ## Forcing CSRF validation

tests/test_testing.py

@@ -263,6 +263,26 @@ def test_explicitly_enforce_csrf_checks(self):
         assert response.status_code == 403
         assert response.data == expected
 
+    def test_transform_factory_django_request_to_drf_request(self):
+        from rest_framework.views import APIView
+
+        factory = APIRequestFactory()
+
+        class DummyView(APIView):
+            ...
+
+        request = factory.get('/', {'demo': 'test'})
+        DRF_request = DummyView().initialize_request(request)
+        assert DRF_request.query_params == {'demo': ['test']}
+        assert not hasattr(DRF_request, 'accepted_media_type')
+
+        DummyView().initial(DRF_request)
+        assert DRF_request.accepted_media_type == 'application/json'
+
+        request = factory.post('/', {'example': 'test'})
+        DRF_request = DummyView().initialize_request(request)
+        assert DRF_request.data.get('example') == 'test'
+
     def test_invalid_format(self):
         """
         Attempting to use a format that is not configured will raise an