tdd-plan

Describe the desired feature or behavior change and let the skill analyze your codebase and existing tests. It clarifies ambiguous decisions, then writes a plan file in .plans/ with ordered test cases you can execute with the implement skill or /tdd.

tdd-plan covers application code changes with automatically testable behavior, producing ordered failing-test-first cases. Documentation, configuration, CI/CD, and infrastructure tasks have no testable behavior and should use the work-plan skill instead.

Skip TDD planning when no test case can fail before the change and pass after it, such as writing documentation, restructuring comments, or changing configuration and infrastructure. The skill will decline and suggest work-plan in those cases.

Test cases progress from the simplest case, like empty input, through basic valid cases to complex combinations, with edge cases and error conditions last. Each test validates one behavior through the public API and builds on previous tests.

Yes, structural changes appear as separate Refactor items placed immediately before the first Test item that depends on them. Refactor items must not change behavior and are never mixed with behavioral changes in a single item.

The skill prints the exact plan filename and .plans/ path. Typing go in the same session continues execution via the implement skill, or you can run /tdd with the filename in a later session.