diff --git a/tests/sample.conf b/tests/sample.conf
index 3a6bc8c0..95c1a478 100644
--- a/tests/sample.conf
+++ b/tests/sample.conf
@@ -12,7 +12,13 @@ auth_prefix = /auth/
 #auth_ssl = no
 #auth_prefix = /v2.0/
 
-# Primary functional test account (needs admin access to the account)
+# Primary functional test account (needs admin access to the account).
+# By default the tests use a swiftclient.client.Connection instance with user
+# attribute set to 'account:username' based on the options 'account' and
+# 'username' specified below. This can be overridden for auth systems that
+# expect a different form of user attribute by setting the option
+# 'account_username'.
+# account_username = test_tester
 account = test
 username = tester
 password = testing