Add tests & workaround

backend/settings.py

@@ -110,3 +110,5 @@
 # https://docs.djangoproject.com/en/5.1/ref/settings/#default-auto-field
 
 DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'
+
+MEDIA_URL = "http://testserver/"

file/tests.py

@@ -1,3 +1,95 @@
+import json
+
+from django.contrib.auth.models import User
+from django.core.files.uploadedfile import SimpleUploadedFile
 from django.test import TestCase
 
-# Create your tests here.
+from .models import ModelOuter, ModelInner, MediaFile
+
+
+class IsStr:
+    def __eq__(self, other):
+        return isinstance(other, str)
+
+
+class TestOuterViewSet(TestCase):
+    maxDiff = None
+
+    def test_nested(self):
+        user = User.objects.create_user(
+            username="test",
+        )
+        inner_file = MediaFile.objects.create(
+            file=SimpleUploadedFile("inner.txt", b"test"),
+            owner=user,
+        )
+        inner_obj = ModelInner.objects.create(
+            file=inner_file,
+        )
+        outer_file = MediaFile.objects.create(
+            file=SimpleUploadedFile("outer.txt", b"test"),
+            owner=user,
+        )
+        outer_obj = ModelOuter.objects.create(
+            inner=inner_obj,
+            file=outer_file,
+        )
+        response = self.client.get(
+            f"/outer/{outer_obj.pk}/", content_type="application/json"
+        )
+        self.assertEqual(response.status_code, 200)
+        body = json.loads(response.content)
+        self.assertDictEqual(
+            body,
+            {
+                "id": outer_obj.pk,
+                "file": {
+                    "id": str(outer_file.pk),
+                    "file": f"http://testserver/media_files/{outer_file.pk}.txt",
+                    "owner": user.pk,
+                    "created_at": IsStr(),
+                },
+                "inner": {
+                    "id": inner_obj.pk,
+                    "file": {
+                        "id": str(inner_file.pk),
+                        "file": f"http://testserver/media_files/{inner_file.pk}.txt",
+                        "owner": user.pk,
+                        "created_at": IsStr(),
+                    },
+                },
+            },
+        )
+
+
+class TestInnerViewSet(TestCase):
+    maxDiff = None
+
+    def test_nested(self):
+        user = User.objects.create_user(
+            username="test",
+        )
+        inner_file = MediaFile.objects.create(
+            file=SimpleUploadedFile("inner.txt", b"test"),
+            owner=user,
+        )
+        inner_obj = ModelInner.objects.create(
+            file=inner_file,
+        )
+        response = self.client.get(
+            f"/inner/{inner_obj.pk}/", content_type="application/json"
+        )
+        self.assertEqual(response.status_code, 200)
+        body = json.loads(response.content)
+        self.assertDictEqual(
+            body,
+            {
+                "id": inner_obj.pk,
+                "file": {
+                    "id": str(inner_file.pk),
+                    "file": f"http://testserver/media_files/{inner_file.pk}.txt",
+                    "owner": user.pk,
+                    "created_at": IsStr(),
+                },
+            },
+        )