diff --git a/pre_commit_hooks/tests_should_end_in_test.py b/pre_commit_hooks/tests_should_end_in_test.py
index 58010d3..14c672e 100644
--- a/pre_commit_hooks/tests_should_end_in_test.py
+++ b/pre_commit_hooks/tests_should_end_in_test.py
@@ -1,11 +1,16 @@
 from __future__ import print_function
 
+import argparse
 import sys
 
 
 def validate_files(argv=None):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*')
+    args = parser.parse_args(argv)
+
     retcode = 0
-    for filename in argv:
+    for filename in args.filenames:
         if (
                 not filename.endswith('_test.py') and
                 not filename.endswith('__init__.py') and