test-ukify: add tests for an empty argument

src/ukify/test/test_ukify.py

@@ -144,6 +144,11 @@ def test_apply_config(tmp_path):
     assert ns.phase_path_groups == [['enter-initrd:leave-initrd:sysinit:ready:shutdown:final']]
 
 def test_parse_args_minimal():
+    try:
+        ukify.parse_args([])
+    except ValueError as e:
+        print(f'expected failure: {e}')
+
     opts = ukify.parse_args('arg1 arg2'.split())
     assert opts.linux == pathlib.Path('arg1')
     assert opts.initrd == [pathlib.Path('arg2')]