# tc39/test262

Official ECMAScript Conformance Test Suite

Repository: https://github.com/tc39/test262
Canonical: https://ross.abutalabs.com/products/test262
Language: JavaScript
License: NOASSERTION
License Family: other
Topics: tc39, js, tests, javascript
Last push: 2026-08-25T09:27:35+00:00

## Health v2 (maintenance only)
Score: 95/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 99, release rhythm 87, longevity 100
- inputs: {"age_days": 4606, "days_push": 8, "days_rel": 8, "gap_med": 0, "n_releases_24m": 256}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2813, forks 558 (observed 2026-08-28T04:07:23.745118+00:00)

## What it is
Test262 is the official conformance test suite for the ECMAScript (JavaScript) language specifications, including ECMA-262, ECMA-402, and ECMA-404. It contains over 50,000 test files used to verify that JavaScript engines, parsers, and runtimes correctly implement the specification.

## Use cases
- verify a JavaScript engine conforms to the ECMAScript spec
- test a new JS runtime implementation against the official test suite
- check parser compliance with ECMAScript grammar
- validate internationalization API behavior in a JS engine
- write conformance tests for a new Stage 4 language proposal
- compare spec compliance across JavaScript engines

## When to choose
- you are building or maintaining a JavaScript engine, parser, or runtime
- you need to verify spec compliance for a Stage 4 proposal implementation
- you want the authoritative, comprehensive ECMAScript test corpus

## When to avoid
- you need unit tests for your own application code
- you want a general-purpose JavaScript testing framework like Jest or Mocha
- you need browser end-to-end testing

## Facets
- artifact type: dataset
- maturity: active
- function: testing, e2e-testing, parser, interpreter
- domain: programming-languages, testing, developer-tools
- platform: cli, cross-platform
- tags: ecmascript, conformance-suite, javascript-engine, tc39, spec-compliance, test-runner, localization, nodejs

## Member repositories
- tc39/test262 (main) score 95

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:07:23.745118+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T08:13:31.090934+00:00, confidence not recorded.
  - readme: https://github.com/tc39/test262 (fetched 2026-08-28T04:07:23.745118+00:00, sha 9e9c5bbc1696)
- Data as of 2026-08-30T08:39:29.467469+00:00.