Use Matt Pocock's TDD Skills for Vertical Slice Test-Driven Development

This article introduces Matt Pocock's tdd Skill constrained programming Agent that follows vertical slice TDD: first agree on the public seams, then write exactly one failing test and just enough implementation code to pass it each time. Based on GitHub's SKILL.md, tests.md, mocking.md and aihero.dev, the article sorts out the testing standards, three anti-patterns, mocking boundaries, installation methods for Cursor / Claude Code / Codex, as well as restrictions such as refactoring being moved to code review and not suitable for glue code.