- Introduced an `assert` field in the test case structure to allow for custom assertion rules, providing flexibility in output validation.
- Defined various assertion types, including `equals`, `contains`, `not_contains`, `json_path`, `regex`, and `script`, to cater to different validation needs.
- Updated the test runner to utilize the new assertion mechanism, replacing the previous expected output validation with a more robust asserter.
- Enhanced documentation in DESIGN.md to include detailed examples and explanations of the new assertion capabilities, improving clarity for users.
