Index: Lib/test/test_argparse.py
===================================================================
--- Lib/test/test_argparse.py	(revision 83942)
+++ Lib/test/test_argparse.py	(working copy)
@@ -16,6 +16,8 @@
     pass
 
 class TestCase(unittest.TestCase):
+    
+    COLUMNS_ENV_VAR_NAME = "COLUMNS"
 
     def assertEqual(self, obj1, obj2):
         if obj1 != obj2:
@@ -26,8 +28,27 @@
             print(obj2)
         super(TestCase, self).assertEqual(obj1, obj2)
 
+    def setUp(self):
+        self.setUpColumns()
 
+    def tearDown(self):
+        self.tearDownColumns()
+    
+    def setUpColumns(self):
+        # The tests assume that line wrapping occurs at 80 columns, which can be overridden by
+        # the COLUMNS environment variable; to ensure this assumption is true, unset COLUMNS if it
+        # is set and restore it after the test completes
+        if self.COLUMNS_ENV_VAR_NAME in os.environ:
+            self.old_columns = os.environ[self.COLUMNS_ENV_VAR_NAME]
+            del os.environ[self.COLUMNS_ENV_VAR_NAME]
 
+    def tearDownColumns(self):
+        try:
+            value = self.old_columns
+        except AttributeError:
+            return # COLUMNS environment variable must not have been set, so no need to restore
+        os.environ[self.COLUMNS_ENV_VAR_NAME] = value
+
 class TempDirMixin(object):
 
     def setUp(self):