djangorestframework APITestCase does not post files correctly

gistfile1.txt

# This case works, using django.test.TestCase
# It creates the output:
# Good request: {'SERVER_PORT': '80', 'REQUEST_METHOD': 'POST', 'wsgi.url_scheme': 'http', 'CONTENT_LENGTH': 158, 'wsgi.input': <django.test.client.FakePayload object at 0x7f79b8287f28>, 'PATH_INFO': '/api/v0/dataset/upload', 'CONTENT_TYPE': 'multipart/form-data; boundary=BoUnDaRyStRiNg', 'QUERY_STRING': ''}

class DatasetAPITest2(TestCase):
    """Tests for uploading files to the dataset API.
    This has to be a django.test.TestCase because APITestCase doesn't appear
    to submit multipart/form-data properly, """

    @classmethod
    def setUpTestData(cls):
        # Set up test user auth and token.
        user = User.objects.create_superuser(username="testadmin", 
            email="test@foo.org", password="testpass")

    def setUp(self):
        self.user = User.objects.get(username="testadmin")
        self.client.login(username='testadmin', password='testpass')

    def test_dataset_list_post(self):
        "Tests using post to create a dataset."
        testfile = io.StringIO("Test faux-file")
        url = reverse('client_api:dataset_upload')
        response = self.client.post(url, {"file":testfile})
        print("Good request:", response.request)
        self.assertEqual(response.status_code, status.HTTP_204_NO_CONTENT)

# This case has identical code and is set to use the multipart/form-data content type
# (instead of the default json content type, which doesn't handle file uploads gracefully)
# but using the rest_framework.test.APITestCase class.
# It produces the following output:
# Flawed request: {'wsgi.url_scheme': 'http', 'QUERY_STRING': '', 'PATH_INFO': '/api/v0/dataset/upload', 'REQUEST_METHOD': 'POST', 'CONTENT_TYPE': 'multipart/form-data', 'SERVER_PORT': '80', 'wsgi.input': <django.test.client.FakePayload object at 0x7f2b0b6e7780>, 'CONTENT_LENGTH': 49}
# ======================================================================
# FAIL: test_dataset_list_post (client_api.tests.DatasetAPITest)
# Tests using post to create a dataset.
# ----------------------------------------------------------------------
# Traceback (most recent call last):
#   File "/home/user/server/src/client_api/tests.py", line 182, in test_dataset_list_post
#     self.assertEqual(response.status_code, status.HTTP_200_OK)
# AssertionError: 400 != 200

class DatasetAPITest(APITestCase):
    @classmethod
    def setUpTestData(cls):
        # Set up test user auth and token.
        user = User.objects.create_superuser(username="testadmin", 
            email="test@foo.org", password="testpass")

    def setUp(self):
        self.user = User.objects.get(username="testadmin")
        self.client.login(username='testadmin', password='testpass')

    def test_dataset_list_post(self):
        "Tests using post to create a dataset."
        testfile = io.StringIO("Test faux-file")
        url = reverse('client_api:dataset_upload')
        response = self.client.post(url, {"file":testfile},
            content_type='multipart/form-data')
        print("Flawed request:", response.request)
            #content_type='application/x-www-form-urlencoded')
        self.assertEqual(response.status_code, status.HTTP_200_OK)
        self.assertEqual(response.data, testData)

# The view that the request is going to
class DatasetUploadView(APIView):
    parser_classes = (FormParser, MultiPartParser, FileUploadParser)
    def post(self, request, format=None):
        print("Request:", request.data)
        file_obj = request.FILES['file']
        print(file_obj)
        return Response("right", status=204)