diff --git a/tests/storage/test__init__.py b/tests/storage/test__init__.py
new file mode 100644
index 000000000..b763d395c
--- /dev/null
+++ b/tests/storage/test__init__.py
@@ -0,0 +1,48 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import sys
+
+from twisted.internet import defer
+
+import tests.unittest
+import tests.utils
+
+
+class InitTestCase(tests.unittest.TestCase):
+    def __init__(self, *args, **kwargs):
+        super(InitTestCase, self).__init__(*args, **kwargs)
+        self.store = None  # type: synapse.storage.DataStore
+
+    @defer.inlineCallbacks
+    def setUp(self):
+        hs = yield tests.utils.setup_test_homeserver()
+        hs.config.max_mau_value = 50
+        hs.config.limit_usage_by_mau = True
+        self.store = hs.get_datastore()
+
+    @defer.inlineCallbacks
+    def test_count_monthly_users(self):
+        count = yield self.store.count_monthly_users()
+        self.assertEqual(0, count)
+        yield self.store.insert_client_ip(
+            "@user:server1", "access_token", "ip", "user_agent", "device_id"
+        )
+
+        yield self.store.insert_client_ip(
+            "@user:server2", "access_token", "ip", "user_agent", "device_id"
+        )
+        count = self.store.count_monthly_users()
+
+        self.assertEqual(2, count)