diff --git a/djrill/tests/mock_backend.py b/djrill/tests/mock_backend.py
index 3e4546b..5003250 100644
--- a/djrill/tests/mock_backend.py
+++ b/djrill/tests/mock_backend.py
@@ -14,7 +14,7 @@ class DjrillBackendMockAPITestCase(TestCase):
             self.content = content
 
     def setUp(self):
-        self.patch = patch('requests.post')
+        self.patch = patch('requests.post', autospec=True)
         self.mock_post = self.patch.start()
         self.mock_post.return_value = self.MockResponse()
 
@@ -28,6 +28,25 @@ class DjrillBackendMockAPITestCase(TestCase):
         self.patch.stop()
         settings.EMAIL_BACKEND = self.original_email_backend
 
+    def assert_mandrill_called(self, endpoint):
+        """Verifies the (mock) Mandrill API was called on endpoint.
+
+        endpoint is a Mandrill API, e.g., "/messages/send.json"
+        """
+        # This assumes the last (or only) call to requests.post is the
+        # Mandrill API call of interest.
+        if self.mock_post.call_args is None:
+            raise AssertionError("Mandrill API was not called")
+        (args, kwargs) = self.mock_post.call_args
+        try:
+            post_url = kwargs.get('url', None) or args[0]
+        except IndexError:
+            raise AssertionError("requests.post was called without an url (?!)")
+        if not post_url.endswith(endpoint):
+            raise AssertionError(
+                "requests.post was not called on %s\n(It was called on %s)"
+                % (endpoint, post_url))
+
     def get_api_call_data(self):
         """Returns the data posted to the Mandrill API.
 
@@ -36,9 +55,10 @@ class DjrillBackendMockAPITestCase(TestCase):
         if self.mock_post.call_args is None:
             raise AssertionError("Mandrill API was not called")
         (args, kwargs) = self.mock_post.call_args
-        if 'data' not in kwargs:
-            raise AssertionError("requests.post was called without data kwarg "
-                                 "-- Maybe tests need to be updated for backend changes?")
-        return json.loads(kwargs['data'])
+        try:
+            post_data = kwargs.get('data', None) or args[1]
+        except IndexError:
+            raise AssertionError("requests.post was called without data")
+        return json.loads(post_data)
 
 
diff --git a/djrill/tests/test_mandrill_send.py b/djrill/tests/test_mandrill_send.py
index 9bce8be..96c4231 100644
--- a/djrill/tests/test_mandrill_send.py
+++ b/djrill/tests/test_mandrill_send.py
@@ -15,6 +15,7 @@ class DjrillBackendTests(DjrillBackendMockAPITestCase):
     def test_send_mail(self):
         mail.send_mail('Subject here', 'Here is the message.',
             'from@example.com', ['to@example.com'], fail_silently=False)
+        self.assert_mandrill_called("/messages/send.json")
         data = self.get_api_call_data()
         self.assertEqual(data['message']['subject'], "Subject here")
         self.assertEqual(data['message']['text'], "Here is the message.")
@@ -54,6 +55,7 @@ class DjrillBackendTests(DjrillBackendMockAPITestCase):
             headers={'Reply-To': 'another@example.com',
                      'X-MyHeader': 'my value'})
         email.send()
+        self.assert_mandrill_called("/messages/send.json")
         data = self.get_api_call_data()
         self.assertEqual(data['message']['subject'], "Subject")
         self.assertEqual(data['message']['text'], "Body goes here")
@@ -78,6 +80,7 @@ class DjrillBackendTests(DjrillBackendMockAPITestCase):
             'from@example.com', ['to@example.com'])
         email.attach_alternative(html_content, "text/html")
         email.send()
+        self.assert_mandrill_called("/messages/send.json")
         data = self.get_api_call_data()
         self.assertEqual(data['message']['text'], text_content)
         self.assertEqual(data['message']['html'], html_content)
@@ -271,6 +274,7 @@ class DjrillMandrillFeatureTests(DjrillBackendMockAPITestCase):
         that your Mandrill account settings apply by default.
         """
         self.message.send()
+        self.assert_mandrill_called("/messages/send.json")
         data = self.get_api_call_data()
         self.assertFalse('from_name' in data['message'])
         self.assertFalse('track_opens' in data['message'])