Add tests for the --preferred-challenges cli parser

certbot/tests/cli_test.py

@@ -423,6 +423,18 @@ class CLITest(unittest.TestCase):  # pylint: disable=too-many-public-methods
         namespace = parse(long_args)
         self.assertEqual(namespace.domains, ['example.com', 'another.net'])
 
+    def test_preferred_challenges(self):
+        from acme.challenges import HTTP01, TLSSNI01, DNS01
+        parse = self._get_argument_parser()
+
+        short_args = ['--preferred-challenges', 'http, tls-sni-01, dns']
+        namespace = parse(short_args)
+
+        self.assertEqual(namespace.pref_challs, [HTTP01, TLSSNI01, DNS01])
+
+        short_args = ['--preferred-challenges', 'jumping-over-the-moon']
+        self.assertRaises(argparse.ArgumentTypeError, parse, short_args)
+
     def test_server_flag(self):
         parse = self._get_argument_parser()
         namespace = parse('--server example.com'.split())