Ensure `_resolve_model` does not return `None`

1 files changed, 33 insertions, 0 deletions

diff --git a/tests/test_utils.py b/tests/test_utils.py
index 96c5f997..0bdb36bb 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -7,6 +7,8 @@ from rest_framework.utils.breadcrumbs import get_breadcrumbs
 from rest_framework.views import APIView
 from tests.models import BasicModel
 
+import rest_framework.utils.model_meta
+
 
 class Root(APIView):
     pass
@@ -130,3 +132,34 @@ class ResolveModelTests(TestCase):
     def test_resolve_improper_string_representation(self):
         with self.assertRaises(ValueError):
             _resolve_model('BasicModel')
+
+
+class ResolveModelWithPatchedDjangoTests(TestCase):
+    """
+    Test coverage for when Django's `get_model` returns `None`.
+
+    Under certain circumstances Django may return `None` with `get_model`:
+    http://git.io/get-model-source
+
+    It usually happens with circular imports so it is important that DRF
+    excepts early, otherwise fault happens downstream and is much more
+    difficult to debug.
+
+    """
+
+    def setUp(self):
+        """Monkeypatch get_model."""
+        self.get_model = rest_framework.utils.model_meta.models.get_model
+
+        def get_model(app_label, model_name):
+            return None
+
+        rest_framework.utils.model_meta.models.get_model = get_model
+
+    def tearDown(self):
+        """Revert monkeypatching."""
+        rest_framework.utils.model_meta.models.get_model = self.get_model
+
+    def test_blows_up_if_model_does_not_resolve(self):
+        with self.assertRaises(ValueError):
+            _resolve_model('tests.BasicModel')