Add test

Author: mbriand

Lib/test/test_readline.py

@@ -405,6 +405,15 @@ def test_write_read_limited_history(self):
         # So, we've only tested that the read did not fail.
         # See TestHistoryManipulation for the full test.
 
+    def test_environment_is_not_modified(self):
+        # os.environ contains enviroment at the time "os" module was loaded, so
+        # before the "readline" module is loaded.
+        original_env = dict(os.environ)
+
+        # Force refresh of os.environ and make sure it is the same as before the
+        # refresh.
+        os.reload_environ()
+        self.assertEqual(dict(os.environ), original_env)
 
 @unittest.skipUnless(support.Py_GIL_DISABLED, 'these tests can only possibly fail with GIL disabled')
 class FreeThreadingTest(unittest.TestCase):