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Dunqing
b60f8a7c14
monitor-oxc's Test262 job fails on every run because `cargo coverage
runtime` no longer matches `runtime.snap`. The runtime suite skips the
cases V8's `test262.status` lists as failing, and it fetches that file
from V8's `main` branch at run time. On 2026-10-09 V8 landed
`03af3c3548` ("[scopes] Reject var arguments in parameter eval") and
removed the 88 `language/eval-code/direct/*declare-arguments*` entries.
Node 26.5 bundles V8 14.6.202, which predates that fix, so those 88
cases now run and fail with `Expected a SyntaxError to be thrown`.
The skip list exists to hide bugs of the engine that executes the cases,
and that engine is Node's V8, not V8 `main`. `main` is wrong in both
directions: it un-skips cases V8 fixed after Node's branch cut, and it
skips 236 entries for test262 files newer than the pinned checkout.
The list is now fetched at the V8 version reported by `node -p
process.versions.v8` (`14.6.202.34`, which V8 tags on GitHub), falling
back to `main` only when that tag does not exist. The gitignored cache
file carries the version in its name so a Node bump cannot serve a stale
list.
With the pinned list the snapshot only changes when the test262 pin or
`.node-version` moves. Regenerated against Node 26.5.0 it adds nothing
and drops: four `delete/super-property-uninitialized-this` cases that V8
fixed upstream after 14.6, the `typeof/symbol.js` timeout, and the two
`bigint-and-number-extremes` minify cases that #27656 fixed (the regular
CI does not run the runtime suite, so that PR could not update the
snapshot):
| skip list | cases | passed | new failures |
| --- | --- | --- | --- |
| V8 `main` today | 18369 | 17307 | 88 |
| V8 `14.6.202.34` | 18277 | 17306 | 0 |
Written with Claude Code; reviewed and tested by me.
Coverage tests
Tools are tested against test262, babel and TypeScript for conformance.
Clone the test repositories beforehand:
just submodules
Development
# full run
cargo coverage
# run a single tool against its supported conformance suites
cargo coverage parser
cargo coverage transformer
cargo coverage minifier
# run in watch
cargo watch -x 'coverage minifier'
# filter for a file path
cargo watch -x 'coverage minifier --filter filter-file-path'
# find crash scene by turning off rayon and print out the test cases in serial
cargo coverage --debug
# Run after submodules are updated
UPDATE_SNAPSHOT=1 just c