opencode/packages/codemode/test/test262-string.md

Test262 String Coverage

The String tests adapt Test262 at revision 250f204f23a9249ff204be2baec29600faae7b75. They cover CodeMode's 32 exposed instance methods and two static methods using primitive receivers, accepted argument types, and deterministic behavior. Each executable case names its exact upstream source path. LICENSE.test262 contains the upstream BSD terms.

This is coverage of CodeMode's bounded String surface, not a claim of ECMAScript or Test262 conformance. One upstream file may contain both adapted and inapplicable assertions, so a cited source means only that the represented assertions were adapted.

Inventory

The relevant upstream directories contain 1,048 files: 1,009 core built-in files, 29 Annex B files for exposed methods, and 10 Intl localeCompare files. The executable suite adapts assertions from 298 distinct sources.

API	Upstream files	Adapted sources
String.fromCharCode	17	6
String.fromCodePoint	11	4
String.prototype.at	11	5
String.prototype.charAt	30	9
String.prototype.charCodeAt	25	4
String.prototype.codePointAt	16	6
String.prototype.concat	22	1
String.prototype.endsWith	27	13
String.prototype.includes	27	12
String.prototype.indexOf	47	8
String.prototype.lastIndexOf	25	1
String.prototype.localeCompare	23	1
String.prototype.match	52	9
String.prototype.matchAll	26	1
String.prototype.normalize	14	3
String.prototype.padEnd	13	4
String.prototype.padStart	13	4
String.prototype.repeat	16	4
String.prototype.replace	56	16
String.prototype.replaceAll	46	12
String.prototype.search	44	10
String.prototype.slice	38	11
String.prototype.split	121	50
String.prototype.startsWith	21	7
String.prototype.substr	15	6
String.prototype.substring	46	12
String.prototype.toLowerCase	30	5
String.prototype.toString	7	1
String.prototype.toUpperCase	26	3
String.prototype.trim	129	66
String.prototype.trimEnd	23	2
String.prototype.trimLeft	4	0
String.prototype.trimRight	4	0
String.prototype.trimStart	23	2

Exclusions

Assertions are not adapted when they test behavior outside CodeMode's documented String surface:

• Function metadata, property descriptors, constructibility, prototype mutation, or cross-realm identity.
• The trimLeft/trimRight Test262 files assert prototype function identity, which CodeMode does not expose. Their supported call behavior remains covered by CodeMode-specific tests.
• Boxed strings, generic receivers, custom coercion objects, Symbols, BigInts, or argument types CodeMode rejects.
• Symbol-based RegExp dispatch, custom matchers, species constructors, or iterator protocol details. CodeMode materializes matchAll results instead of exposing iterators.
• Locale selection and options. CodeMode deliberately uses the host default locale and ignores those arguments.
• Test262 harness behavior or setup syntax unavailable in the confined interpreter.
• Function-replacer behavior that is covered by CodeMode-specific tests for sequential callbacks, async tool calls, result coercion, diagnostics, and sandbox boundaries.
• Assertions requiring an exact native error type when CodeMode deliberately exposes only its safe runtime error.

Handwritten tests remain where they specify CodeMode behavior rather than ordinary ECMAScript String semantics.