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

Test262 Array Coverage

The Array tests adapt Test262 at revision 250f204f23a9249ff204be2baec29600faae7b75. They cover CodeMode's 35 exposed instance methods and three static methods using actual arrays, accepted argument types, deterministic behavior, and CodeMode's materialized collection conventions. Each executable case names its exact upstream source path. LICENSE.test262 contains the upstream BSD terms.

This is coverage of CodeMode's bounded Array 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 38 relevant upstream API directories contain 2,837 files. The executable suite adapts assertions from 83 distinct sources.

API	Upstream files	Adapted sources
Array.prototype.map	216	3
Array.prototype.filter	242	3
Array.prototype.find	23	4
Array.prototype.findIndex	23	3
Array.prototype.findLast	24	3
Array.prototype.findLastIndex	24	3
Array.prototype.some	219	2
Array.prototype.every	218	2
Array.prototype.includes	30	2
Array.prototype.join	23	2
Array.prototype.reduce	260	3
Array.prototype.reduceRight	260	3
Array.prototype.flatMap	24	2
Array.prototype.forEach	190	2
Array.prototype.sort	54	3
Array.prototype.toSorted	21	4
Array.prototype.slice	71	1
Array.prototype.concat	69	3
Array.prototype.indexOf	201	2
Array.prototype.lastIndexOf	198	2
Array.prototype.at	13	3
Array.prototype.flat	19	2
Array.prototype.reverse	18	1
Array.prototype.toReversed	17	2
Array.prototype.with	21	2
Array.prototype.push	24	1
Array.prototype.pop	23	1
Array.prototype.shift	20	1
Array.prototype.unshift	22	1
Array.prototype.splice	81	3
Array.prototype.fill	22	3
Array.prototype.copyWithin	39	2
Array.prototype.keys	12	1
Array.prototype.values	12	1
Array.prototype.entries	12	1
Array.from	47	3
Array.isArray	29	2
Array.of	16	1

Exclusions

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

• Function metadata, property descriptors, constructibility, prototype mutation, species constructors, or cross-realm identity.
• Generic receivers, detached methods, .call, .apply, boxed values, custom coercion objects, Symbols, BigInts, proxies, accessors, frozen arrays, typed arrays, or ArrayBuffers.
• Array.from mappers, custom iterables, constructor substitution, and iterator-closing behavior.
• Native iterator identity, .next(), completion records, or live iterator mutation. CodeMode deliberately materializes keys, values, and entries as arrays.
• Sparse-array assertions that depend on literal elisions or inherited indexed properties. CodeMode's confined data model does not preserve those prototype and hole semantics at every boundary.
• Argument coercions outside the accepted schema-like surface. Numeric positions must be numbers and join separators must be strings.
• Exact native error brands where CodeMode exposes a safe runtime error instead.
• Async/effectful callbacks, circular-data rejection, sandbox-value identity, diagnostics, and host-boundary behavior. Those remain covered by CodeMode-specific tests.

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