Use when writing tests for functional code, when tests need heavy mocking or a database, when deciding what to test, or turning a claimed law into a property.
Install
npx skills add yutna/functional-design-skills --skill functional-testing-functional-codenpx skills add yutna/functional-design-skills --skill functional-testing-functional-code -a claude-code -gnpx skills add yutna/functional-design-skills --skill functional-testing-functional-code -a codex -ggemini skills install https://github.com/yutna/functional-design-skills.git --path plugin/skills/functional-testing-functional-codegh skill install yutna/functional-design-skills functional-testing-functional-codegit clone --depth 1 https://github.com/yutna/functional-design-skills /tmp/yutna__functional-design-skills
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/yutna__functional-design-skills/plugin/skills/functional-testing-functional-code ~/.claude/skills/functional-testing-functional-code # Claude Code
cp -R /tmp/yutna__functional-design-skills/plugin/skills/functional-testing-functional-code ~/.agents/skills/functional-testing-functional-code # Codex, Cursor, Gemini CLI, Copilot, OpenCode