Add missed files for test.

tests/browsable_api/models.py

+from django.db import models
+
+
+class Foo(models.Model):
+    name = models.CharField(max_length=30)
+
+
+class Bar(models.Model):
+    foo = models.ForeignKey("Foo", editable=False)

tests/browsable_api/serializers.py

+from .models import Foo, Bar
+from rest_framework.serializers import HyperlinkedModelSerializer, HyperlinkedIdentityField
+
+
+class FooSerializer(HyperlinkedModelSerializer):
+    bar = HyperlinkedIdentityField(view_name='bar-list')
+
+    class Meta:
+        model = Foo
+
+
+class BarSerializer(HyperlinkedModelSerializer):
+    class Meta:
+        model = Bar