Behavior-Driven Development (BDD)

Produces feature files that read like behavior, step definitions that don't leak implementation, and an honest call on when BDD pays for itself. The body is tool-agnostic — load the relevant reference for Vitest or Playwright.

When to use this skill

• The user names a BDD concept: BDD, Gherkin, Cucumber, .feature, Given/When/Then, Scenario Outline, Background, Rule, step definitions, executable specifications, living documentation, Three Amigos, Example Mapping.
• The user wants to turn acceptance criteria into tests, write tests in plain English, or refactor a .feature file.
• Vitest + BDD → also load references/vitest.md. Playwright + BDD → also load references/playwright.md.
• Setting up either from zero → load references/install-vitest.md or references/install-playwright.md.

Skip for: unit tests with no business audience, performance/load tests, internal refactors, or generic test-framework questions.

Gherkin cheat sheet