This commit refactors the test suites for the `crypt` and `trix` packages to follow the Good, Bad, and Ugly testing strategy.
- `_Good` tests cover the ideal "happy path" scenarios.
- `_Bad` tests cover expected failure scenarios with well-formed but invalid inputs.
- `_Ugly` tests cover malicious or malformed inputs designed to cause crashes or panics.
This new testing structure makes the test suite more organized, comprehensive, and robust.
Additionally, this commit includes a bug fix for the `Luhn` function, which now correctly handles empty and single-digit strings.
