Reverts docstring quoting syntax.
diff --git a/tests/test_strings.py b/tests/test_strings.py
index a2f9483..001456d 100644
--- a/tests/test_strings.py
+++ b/tests/test_strings.py
@@ -1,4 +1,4 @@
-"""Tests string operations."""
+'''Tests string operations.'''
 
 from __future__ import absolute_import