Fix missing test coverage.

mimic/test/helpers.py

@@ -6,6 +6,8 @@
 
 import json
 
+from six import string_types
+
 from zope.interface import implementer
 
 from twisted.test.proto_helpers import StringTransport, MemoryReactor
@@ -184,7 +186,7 @@ def json_request(testCase, rootResource, method, uri, body=b"",
     Issue a request with a JSON body (if there's a body at all) and return
     synchronously with a tuple of ``(response, JSON response body)``
     """
-    if body != "":
+    if not isinstance(body, string_types):
         body = json.dumps(body)
 
     d = request(testCase, rootResource, method, uri, body, baseURI, headers)

mimic/test/test_nova.py

@@ -941,7 +941,7 @@ def test_set_metadata_with_invalid_json_body_fails(self):
         When setting metadata with an invalid request body (not a dict), it
         should return an HTTP status code of 400:malformed request body
         """
-        self.assert_malformed_body(*self.set_metadata("meh"))
+        self.assert_malformed_body(*self.set_metadata('meh'))
 
     def test_set_metadata_with_invalid_metadata_object(self):
         """
@@ -1049,6 +1049,21 @@ def test_set_metadata_item_with_wrong_key_fails(self):
             *self.set_metadata_item({}, "meh",
                                     {"metadata": {"meh": "value"}}))
 
+    def test_set_metadata_item_with_mismatching_key_and_body(self):
+        """
+        When setting metadata item, the key in the 'meta' dictionary needs to
+        match the key in the URL, or a special 400 response is returned.
+        """
+        response, body = self.set_metadata_item(
+            {}, "key", {"meta": {"notkey": "value"}})
+        self.assertEqual(response.code, 400)
+        self.assertEqual(body, {
+            "badRequest": {
+                "message": "Request body and URI mismatch",
+                "code": 400
+            }
+        })
+
     def test_set_metadata_item_with_wrong_meta_type_fails(self):
         """
         When setting metadata item without a 'meta' key mapped to not a