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Vitest is the testing framework that makes Jest feel like last decade. Same familiar API (`describe`, `it`, `expect`) but instant startup, native TypeScript support, and hot module reloading for your tests.

What's free: Everything. MIT license. The entire testing framework, all matchers, mocking, coverage, UI mode, browser mode. All free.

Vitest's speed comes from Vite's transformation pipeline. No separate TypeScript compilation step, no Babel config, no jest.config.js with 40 lines of transform rules. Point it at your code and it works. The compatibility with Jest's API means migrating is often just changing imports. The `, ui` mode gives you a browser-based test explorer that's useful.

The catch: if you're not in the Vite ecosystem, some of the speed advantages diminish. The browser testing mode is still maturing. And while the Jest API compatibility is high, it's not 100%. Some Jest plugins and custom matchers need adaptation. For non-Vite projects with heavy Jest customization, the migration cost might not be worth it.

### What's Free Everything. MIT license. Framework, matchers, mocking, code coverage (via v8 or istanbul), UI mode, browser mode, benchmarking, type testing. All free.

### Total Cost $0. No paid tier exists or is planned. Vitest is community-funded through sponsors.

### What You Might Pay For Alongside It - **CI/CD**: GitHub Actions (2,000 min/mo free), GitLab CI (400 min/mo free). Vitest runs here. - **Coverage hosting**: Codecov or Coveralls (free for open source, $10-29/mo for private repos). - **Visual regression**: Percy ($75+/mo) or Chromatic ($149+/mo) for UI screenshot tests. Vitest doesn't do this natively.

### Migration Cost from Jest - Simple projects: 1-2 hours. Change imports, update config. - Complex projects with custom Jest transforms: 4-8 hours. - Projects with custom Jest runners or heavy plugin usage: evaluate case-by-case.

### The Speed Payoff Vitest runs 2-10x faster than Jest on TypeScript projects because it skips the compilation step. On a 500-test suite, that's the difference between 30 seconds and 3-5 seconds. In CI, that's real money saved on build minutes.

Vitest

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