Chai
BDD/TDD assertion library for Node.js and browsers, pairable with Mocha, Jest or Jasmine through should, expect and assert interfaces.
Our Verdict
A capable but aging assertion library, mostly justified when sticking with Mocha-era codebases.
Pros
- Three styles: should, expect, assert for any taste
- Pairs cleanly with Mocha, Jest or Jasmine
- Rich plugin ecosystem: chai-as-promised, sinon-chai
- Readable BDD-style error messages
Cons
- Historically CJS-first, ESM migration has been painful
- Overlap with Jest expect leads to confusion
- Multiple assertion styles hurt team consistency
- Feels dated next to Vitest and native node:test
When to Use Chai
Good fit if you need
- BDD-style expect/should assertions in Node.js test suites
- Chain readable assertions for complex object comparisons
- Pluggable assertion library pairable with Mocha or Jest
- Custom matchers via chai plugins for domain objects
Pricing
Price wrong?Chai Pricing
- Pricing Model
- free
- Free Tier
- Yes
- Entry Price
- —
- Enterprise Available
- No
- Transparency Score
- —
Beta — estimates may differ from actual pricing
Estimated Monthly Cost
$25
Estimated Annual Cost
$300
Estimates are approximate and may not reflect current pricing. Always check the official pricing page.
Project Health
Health Score
10
1 day
31d
90
N/A
MIT
Last checked: 2026-04-21
Lock-in Assessment
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