diff --git a/Lib/idlelib/idle_test/test_browser.py b/Lib/idlelib/idle_test/test_browser.py
index 343d50a6e37bd6..6cfea3888cd6a9 100644
--- a/Lib/idlelib/idle_test/test_browser.py
+++ b/Lib/idlelib/idle_test/test_browser.py
@@ -170,8 +170,7 @@ def test_ondoubleclick(self, fopen):
 
         with mock.patch('os.path.exists', return_value=True):
             mbt.OnDoubleClick()
-            fopen.assert_called()
-            fopen.called_with(fname)
+            fopen.assert_called_once_with(fname)
 
 
 class ChildBrowserTreeItemTest(unittest.TestCase):