Bun Test

ELI5 — The Vibe Check

Bun test is Bun's built-in test runner — Jest-compatible but fast enough to make you question every life choice that led to Vitest. You write the same describe(), it(), expect() tests you already know. Bun just runs them absurdly quickly. No config. No install. Just bun test. It's what happens when a runtime is built by people who were genuinely angry at how slow existing tools were.

Real Talk

bun test is Bun's native test runner, shipping as part of the Bun runtime (no separate install). It supports the Jest/Vitest API surface (describe, it, test, expect, beforeEach, lifecycle hooks, mocking via jest.mock). It runs tests in parallel using Bun's native worker threads and executes TypeScript and JSX natively without a build step. Benchmark comparisons consistently show 10–40x speedups over Jest on large test suites.

When You'll Hear This

"Switched from Jest to bun test — our 800-test suite went from 45 seconds to 3." / "Bun test is Jest-compatible enough that migration was copy-paste and done."