054-design-tdd

# Test-Driven Development Design Guide Java developers through Test-Driven Development for implementation work. **This is an interactive SKILL**. **What is covered in this Skill?** - Maintaining or refining a list of candidate test cases - Selecting the next useful behavior or test case before editing production code - Writing a failing test first to clarify the public interface, API shape, or usage of the code - Writing only enough functional production code to pass the selected test - Refactoring new and existing code while tests remain green - Adding newly discovered test cases to the list without losing the current TDD cycle - Reporting skipped checks, missing tests, and remaining risks when verification is incomplete ## Constraints Keep implementation work inside the red-green-refactor cycle, with one selected behavior driving each small change. - **MUST** read `references/054-design-tdd.md` before applying TDD guidance - **MUST** maintain or refine a test list when more than one behavior, edge case, or question is in scope - **MUST** select the next useful behavior or test case before writing production code - **MUST** write or describe the failing test first and use it to clarify the public interface or usage - **MUST** implement only the functional production code needed to pass the selected failing test - **MUST** refactor new and existing code only after the selected test passes and while keeping tests green - **MUST** report skipped checks, missing tests, and...