Add test to assert set_e2e_device_keys correctly returns False on no-op

tests/storage/test_end_to_end_keys.py

@@ -44,6 +44,21 @@ def test_key_without_device_name(self):
         dev = res["user"]["device"]
         self.assertDictContainsSubset({"keys": json, "device_display_name": None}, dev)
 
+    @defer.inlineCallbacks
+    def test_reupload_key(self):
+        now = 1470174257070
+        json = {"key": "value"}
+
+        yield self.store.store_device("user", "device", None)
+
+        changed = yield self.store.set_e2e_device_keys("user", "device", now, json)
+        self.assertTrue(changed)
+
+        # If we try to upload the same key then we should be told nothing
+        # changed
+        changed = yield self.store.set_e2e_device_keys("user", "device", now, json)
+        self.assertFalse(changed)
+
     @defer.inlineCallbacks
     def test_get_key_with_device_name(self):
         now = 1470174257070