Book: TypeScript in Production — Tooling, Build, and Library Authoring Across Runtimes

Also by me: The TypeScript Library — the 5-book collection

My project: Hermes IDE | GitHub — an IDE for developers who ship with Claude Code and other AI coding tools

Me: xgabriel.com | GitHub

You've seen it. A library has two test scripts in the same

package.json . One says bun test . The other says vitest run .

The CI matrix runs both. The local dev loop runs whichever one

the maintainer typed last. The README does not mention either.

The reason there are two is that the library exports a function

that does some HTTP work, and at some point a maintainer got

tired of waiting for Vitest to spin up to re-check a one-line fix

in a small unit suite. They tried bun test , it felt noticeably

quicker, they kept it. Then a contributor opened a PR that

mocked an ESM dependency the way Vitest's docs describe. It

worked under Vitest.…