Add test case for is_list_view logic

Test reveals my logical use of isinstance is not working as intended.

rest_framework/schemas.py

@@ -142,7 +142,7 @@ def is_list_view(path, method, view):
         return False
     if isinstance(view, mixins.ListModelMixin):
         return True
-    if isinstance(view, generics.RetrieveAPIView):
+    if isinstance(view, mixins.RetrieveModelMixin):
         return False
     # Otherwise when path ends in a variable it is assumed a singular lookup
     path_components = path.strip('/').split('/')

tests/test_schema_helpers.py

@@ -0,0 +1,44 @@
+from django.test import TestCase
+
+from rest_framework import generics, permissions
+from rest_framework import schemas
+from rest_framework.response import Response
+
+
+class ExampleListView(generics.ListAPIView):
+
+    def list(self, request, *args, **kwargs):
+        # Mock actually using models
+        response_list = [
+            {'id': '1'},
+            {'id': '2'},
+            {'id': '3'},
+        ]
+        return Response(response_list)
+
+
+class ExampleRetrieveView(generics.RetrieveAPIView):
+    permission_classes = [permissions.IsAuthenticatedOrReadOnly]
+    serializer_class = None
+
+    def retrieve(self, request, *args, **kwargs):
+        # Mock: do something based on request state
+        data = {'request.user': "A Description of the known request object."}
+        return Response(data)
+
+
+class TestIsListViewLogic(TestCase):
+
+    def test_when_view_is_retrieve_view(self):
+        view = ExampleRetrieveView.as_view()
+        view_url = '^my-profile/?$'
+
+        is_list = schemas.is_list_view(view_url, 'get', view)
+        self.assertFalse(is_list, "Expected a standard RetrieveAPIView to be singular lookup.")
+
+    def test_when_view_is_list_view(self):
+        view = ExampleListView.as_view()
+        view_url = '^my-list/?$'
+
+        is_list = schemas.is_list_view(view_url, 'get', view)
+        self.assertTrue(is_list, "Expected a standard ListAPIView to return list data.")