tc39/test262

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Official ECMAScript Conformance Test Suite

Stars: 2.8k
Forks: 564
Open beginner issues: 3
Indexed issues: 213
Avg merge: 3d 7h
Merged PRs (30d): 10

Dominant language: JavaScript
License: No license data
Last GitHub push: Sep 17, 2026
Latest indexed: Sep 19, 2026
Contributing guide: Contributing guide
Code of conduct: Code of conduct
Beginner labels: help wanted

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213 open issues indexed

Consider adding negative Test For Invalid BigInt literals Open

Difficulty 2/5 1-3 hours Newbie friendliness 78/100

tc39/test262#5133 · 1 comment · Opened Sep 10, 2026
Coverage candidates discovered while implementing Generator semantics in an ECMAScript companion language Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

tc39/test262#5131 · Opened Sep 7, 2026
Uint8Array.prototype.toHex tests do not test for padding Open

Difficulty 1/5 Under an hour Newbie friendliness 90/100

tc39/test262#5130 · Opened Sep 7, 2026
Can we drop test file contents from Engine tests GitHub artifacts? Open

Difficulty 3/5 1-2 days Newbie friendliness 58/100

tc39/test262#5127 · Opened Sep 2, 2026
Testing plan for Thenable-Curtailment (Safe Promise Resolve) Open

Difficulty 5/5 Over a week Newbie friendliness 38/100

tc39/test262#5122 · 1 comment · Opened Aug 31, 2026
create AI policy Open

group process

Difficulty 5/5 Over a week Newbie friendliness 30/100

tc39/test262#5115 · 1 comment · 2 reactions · Opened Aug 24, 2026
annexB block-decl-func-skip-arguments contradicts staging/sm block-scoped-functions-annex-b-arguments Open

Difficulty 2/5 1-3 hours Newbie friendliness 86/100

tc39/test262#5113 · Opened Aug 20, 2026
Negative coverage requested for ArrayBuffer methods Open

Difficulty 3/5 1-2 days Newbie friendliness 68/100

tc39/test262#5064 · 1 comment · 1 reaction · Opened May 27, 2026
Insufficient coverage for Intl.Locale.prototype.getNumberingSystems() Open

tc39/test262#5062 · 1 assignee · Opened May 26, 2026
Support for asynchronous Garbage Collection in host-defined $262.gc() Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

tc39/test262#5029 · 2 comments · Opened Apr 15, 2026
Test plan for deferred re-exports (`export defer`) Open

tc39/test262#5010 · 1 comment · 1 reaction · 1 assignee · Opened Apr 1, 2026
Clarify the use of 'using' as a variable reference expression in for loop conditions Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4961 · 2 comments · Opened Feb 28, 2026
Missing tests for yield in finally block of a generator Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

tc39/test262#4937 · 1 comment · Opened Feb 20, 2026
Probably missing coverage for ECMA-402 ToIntlMathematicalValue Open

coverage

Difficulty 3/5 1-2 days Newbie friendliness 48/100

tc39/test262#4933 · 2 comments · Opened Feb 18, 2026
Test that -u-ca-iso8601 implies hc-h23 Open

Difficulty 2/5 1-3 hours Newbie friendliness 55/100

tc39/test262#4882 · 1 comment · Opened Jan 21, 2026
ESM coverage: async parent executing after rejection in different branch of a graph Open

Difficulty 3/5 1-2 days Newbie friendliness 48/100

tc39/test262#4864 · Opened Jan 14, 2026
test/staging/sm/Date/non-iso.js should be deleted Open

Difficulty 1/5 Under an hour Newbie friendliness 55/100

tc39/test262#4788 · Opened Dec 15, 2025
Filename linter always fails on Windows Open

Difficulty 3/5 1-2 days Newbie friendliness 38/100

tc39/test262#4643 · 1 comment · Opened Nov 6, 2025
Improve error messages from compareArray Open

Difficulty 5/5 Over a week Newbie friendliness 35/100

tc39/test262#4595 · Opened Oct 8, 2025
V8 sync bot: Check why tests moved out of staging were re-synced Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

tc39/test262#4580 · Opened Sep 15, 2025
Possible copy by array test coverage gaps Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4575 · 1 comment · Opened Sep 10, 2025
Add linter that rejects bare module specifiers Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

tc39/test262#4570 · 1 reaction · Opened Sep 2, 2025
`built-ins/RegExp/property-escapes/non-existent-property-value-*` tests use invalid quantifiers, not non-existent property values Open

Difficulty 2/5 1-3 hours Newbie friendliness 68/100

tc39/test262#4555 · 1 reaction · Opened Aug 8, 2025
`Intl.NumberFormat.prototype.format` should allow both with/without spaces around numbers Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4536 · Opened Jul 13, 2025
Add test for extreme Intl Mathematical Values Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4527 · Opened Jul 2, 2025
Testing plan for Immutable ArrayBuffers Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

tc39/test262#4509 · 2 comments · Opened May 29, 2025
Invalid explicit resource management tests in `staging` Open

Difficulty 2/5 1-3 hours Newbie friendliness 58/100

tc39/test262#4498 · Opened May 21, 2025
Check validity of the `acosh-approx.js` test Open

Difficulty 3/5 1-2 days Newbie friendliness 35/100

tc39/test262#4487 · 1 comment · Opened May 14, 2025
Consider helpers for `formatToParts` assertions Open

Difficulty 4/5 3-5 days Newbie friendliness 38/100

tc39/test262#4451 · Opened Apr 9, 2025
Add test for Intl.Locale from "und" Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4444 · 8 comments · 1 reaction · Opened Mar 31, 2025
Should test262/test/intl402/DateTimeFormat/offset-timezone-no-unicode-minus-sign.js fail ONLY if offset time zones are supported? Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4443 · 1 comment · Opened Mar 30, 2025
Lack of tests around destructuring and export statements Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4432 · 1 comment · Opened Mar 19, 2025
Is `harness/typeCoercion.js` used? Open

Difficulty 2/5 1-3 hours Newbie friendliness 42/100

tc39/test262#4429 · 1 comment · Opened Mar 17, 2025
Deal with slow staging/sm tests Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

tc39/test262#4402 · 2 comments · 1 reaction · Opened Feb 18, 2025
Remove useless "Am I really in a script" checks in `import.source` tests Open

tc39/test262#4388 · 2 comments · 1 assignee · Opened Feb 3, 2025
`desc` in .case files cannot start with `[` (even if quoted) Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4384 · Opened Jan 24, 2025
Iterator/concat/next-method-returns-throwing-value-done.js is outdated Open

Difficulty 1/5 Under an hour Newbie friendliness 68/100

tc39/test262#4380 · Opened Jan 16, 2025
Functions tests would benefit from a helper like `verifyNoRestrictedFunctionProperties` Open

Difficulty 5/5 Over a week Newbie friendliness 30/100

tc39/test262#4378 · 1 comment · Opened Jan 13, 2025
staging/sm has a lot of tests that don't use the test262 harness Open

tc39/test262#4376 · 5 comments · 1 reaction · 1 assignee · Opened Jan 10, 2025
Tests in `src/dynamic-import/catch` don't fail if the error is not thrown Open

Difficulty 2/5 1-3 hours Newbie friendliness 55/100

tc39/test262#4373 · Opened Jan 10, 2025
Bug in test/intl402/NumberFormat/currency-digits-nonstandard-notation.js Open

Difficulty 1/5 Under an hour Newbie friendliness 55/100

tc39/test262#4349 · Opened Dec 13, 2024
Missing tests for bindings that shadow globalThis properties Open

coverage help wanted

Difficulty 4/5 3-5 days Newbie friendliness 38/100

tc39/test262#4332 · Opened Nov 23, 2024
Linter should output line numbers Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4319 · Opened Nov 7, 2024
this-value-valid-date.js under test262/built-ins/Date/prototype doesn't test Date.prototype as the this-value Open

Difficulty 1/5 Under an hour Newbie friendliness 35/100

tc39/test262#4317 · Opened Nov 6, 2024
not-a-constructor.js tests should create objects outside the test function Open

Difficulty 1/5 Under an hour Newbie friendliness 65/100

tc39/test262#4316 · Opened Nov 6, 2024
this-value-non-object.js under test262/built-ins/Date/prototype doesn't test BigInts Open

Difficulty 1/5 Under an hour Newbie friendliness 45/100

tc39/test262#4315 · Opened Nov 6, 2024
Decorators: Class decorators are part of the class and their local names must be valid in strict mode. Open

Difficulty 4/5 3-5 days Newbie friendliness 35/100

tc39/test262#4238 · Opened Sep 25, 2024
Harness tests should run when harness source changes Open

Difficulty 2/5 1-3 hours Newbie friendliness 50/100

tc39/test262#4201 · 4 reactions · Opened Aug 17, 2024
Source phase import tests importing from "<do not resolve>" are broken Open

Difficulty 2/5 1-3 hours Newbie friendliness 42/100

tc39/test262#4193 · 1 comment · Opened Aug 13, 2024
Follow-up to Intl.DurationFormat #3912 Open

Difficulty 3/5 1-2 days Newbie friendliness 45/100

tc39/test262#4168 · Opened Jul 24, 2024

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