Auto-generates test files when you write new code. Detects your test framework (RSpec, pytest, Jest, Vitest, PHPUnit, Go testing, ExUnit, Rust) and scaffolds comprehensive test suites covering happy path, edge cases, and error handling. A PostToolUse hook reminds you when edited source files lack a corresponding test file, and the /generate-tests command scans your project for untested code. Matches your project's existing test style, uses factories/fixtures, and mocks external dependencies automatically.