diff --git a/tests/util/test_expiring_cache.py b/tests/util/test_expiring_cache.py
new file mode 100644
index 000000000..31d24adb8
--- /dev/null
+++ b/tests/util/test_expiring_cache.py
@@ -0,0 +1,84 @@
+# -*- coding: utf-8 -*-
+# Copyright 2017 OpenMarket 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.
+
+
+from .. import unittest
+
+from synapse.util.caches.expiringcache import ExpiringCache
+
+from tests.utils import MockClock
+
+
+class ExpiringCacheTestCase(unittest.TestCase):
+
+    def test_get_set(self):
+        clock = MockClock()
+        cache = ExpiringCache("test", clock, max_len=1)
+
+        cache["key"] = "value"
+        self.assertEquals(cache.get("key"), "value")
+        self.assertEquals(cache["key"], "value")
+
+    def test_eviction(self):
+        clock = MockClock()
+        cache = ExpiringCache("test", clock, max_len=2)
+
+        cache["key"] = "value"
+        cache["key2"] = "value2"
+        self.assertEquals(cache.get("key"), "value")
+        self.assertEquals(cache.get("key2"), "value2")
+
+        cache["key3"] = "value3"
+        self.assertEquals(cache.get("key"), None)
+        self.assertEquals(cache.get("key2"), "value2")
+        self.assertEquals(cache.get("key3"), "value3")
+
+    def test_iterable_eviction(self):
+        clock = MockClock()
+        cache = ExpiringCache("test", clock, max_len=5, iterable=True)
+
+        cache["key"] = [1]
+        cache["key2"] = [2, 3]
+        cache["key3"] = [4, 5]
+
+        self.assertEquals(cache.get("key"), [1])
+        self.assertEquals(cache.get("key2"), [2, 3])
+        self.assertEquals(cache.get("key3"), [4, 5])
+
+        cache["key4"] = [6, 7]
+        self.assertEquals(cache.get("key"), None)
+        self.assertEquals(cache.get("key2"), None)
+        self.assertEquals(cache.get("key3"), [4, 5])
+        self.assertEquals(cache.get("key4"), [6, 7])
+
+    def test_time_eviction(self):
+        clock = MockClock()
+        cache = ExpiringCache("test", clock, expiry_ms=1000)
+        cache.start()
+
+        cache["key"] = 1
+        clock.advance_time(0.5)
+        cache["key2"] = 2
+
+        self.assertEquals(cache.get("key"), 1)
+        self.assertEquals(cache.get("key2"), 2)
+
+        clock.advance_time(0.9)
+        self.assertEquals(cache.get("key"), None)
+        self.assertEquals(cache.get("key2"), 2)
+
+        clock.advance_time(1)
+        self.assertEquals(cache.get("key"), None)
+        self.assertEquals(cache.get("key2"), None)