Fix validate_interaction test for required VASP potcar_prefix.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: Zikkying

tests/test_skill_scripts.py

@@ -417,8 +417,8 @@ def test_validate_interaction(self):
         errors, warnings = self.validator.validate_interaction(
             {"type": "vasp", "potcars": {}}
         )
-        self.assertFalse(errors)
-        self.assertTrue(any("potcar_prefix" in warning for warning in warnings))
+        self.assertTrue(any("potcar_prefix" in error for error in errors))
+        self.assertFalse(warnings)
 
     def test_validate_property_required_fields(self):
         cases = (