Test case for cli startup without any arguments

tests/test_cli.py

@@ -11,3 +11,9 @@ def test_no_action():
     args = parse_args(['-l', 'some_path', '-c', 'fake_cookie'])
     assert args.library_path == 'some_path'
     assert args.cookie_file == 'fake_cookie'
+
+
+def test_no_args():
+    with pytest.raises(SystemExit) as ex:
+        parse_args([])
+    assert ex.value.code == 2