diff --git a/requirements.txt b/requirements.txt
index b30b450..e5b93b8 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -16,4 +16,5 @@
 six>=1.10.0 # MIT
 tempest>=17.1.0 # Apache-2.0
 tenacity>=4.4.0 # Apache-2.0
+testtools>=2.2.0 # MIT
 keystoneauth1>=3.3.0 # Apache-2.0