Tooling for running the Test262 conformance suite against JavaScriptCore and for importing new versions of the suite into the tree.

To run the suite, invoke the runner:

./Tools/Scripts/test262-runner --release

The build configuration defaults to --release; pass --debug to use a debug build instead (the two are mutually exclusive). The runner discovers the matching jsc binary under WebKitBuild by default; pass --jsc <path> to use a specific binary instead.

By default, every test is run, results are compared against the checked-in expectations file and the script exits non-zero if any new failures appear (failures already listed in the expectations file are ignored). Reports are written to test262-results/ in the current directory.

If you need to customize the execution, check out ./Tools/Scripts/test262-runner --help for extra commands.

This file controls which tests are skipped and which JSC runtime flags to enable for particular features. Example:

---
# Enable a JSC feature flag for every test that lists the given feature.
# Adds `--<flag>=1` to the jsc command line.
flags:
  SharedArrayBuffer: useSharedArrayBuffer
  Temporal: useTemporal

skip:
  # Skip any test whose metadata lists one of these features.
  features:
    - decorators
    - source-phase-imports
  # Skip tests whose path matches one of these regexes.
  paths:
    - test/staging/Intl402
  # Skip these individual test files.
  files:
    - test/built-ins/Array/prototype/reverse/length-exceeding-integer-limit-with-object.js
  # Skip only under matching build/platform conditions. Each entry's `if`
  # clause may constrain os, os_version, build (release/debug) and sanitizer;
  # files/paths/features are skipped only when the condition matches.
  conditions:
    - if:
        os: macOS
        os_version: 26.4
      features:
        - Atomics
    - if:
        build: debug
      paths:
        - test/built-ins/RegExp/property-escapes

This file records every expected failure. When JSC or Test262 changes, it should be updated so that developers see only the failures they introduce.

Each entry maps a test file to the modes it's expected to fail in (default, strict mode, module or raw), and each mode to the exit code jsc is expected to terminate with:

• 3: the test ran to completion and failed (a failed assertion or an uncaught exception; JSC's EXIT_EXCEPTION).
• 128 + N: jsc was killed by signal N, i.e. it crashed (e.g. 134 SIGABRT, 139 SIGSEGV).
• 1: jsc could not run the test at all, or the runner timed out.

Because the recorded exit code has to match, a test that starts crashing where it previously failed an assertion is still reported as a new failure.

On Linux, the runner uses expectations-linux.yaml instead.

To update the expectations file, run:

./Tools/Scripts/test262-runner --release --save

--save updates entries incrementally: if you run a subset of the suite (for example with --test-only or --filter), only the tests that actually ran are rewritten and the rest of the file is left untouched.

Written to the current directory on every run:

• results.yaml: results for every test that ran.
• summary.txt, summary.yaml, summary.html: pass/fail/skip statistics by feature and by folder.
• index.html: an expandable report of the failures (styled by report.css).

To import a new version of Test262, run the importer. With no arguments, it shallow-clones the canonical upstream repository and updates the JSTests/test262 folder:

./Tools/Scripts/test262-import

It records the imported commit in JSTests/test262/test262-Revision.txt and a list of the changed files in JSTests/test262/latest-changes-summary.txt (which the runner's --latest-import mode reads). If the revision has not changed since the last import, it exits without doing anything.

Run ./Tools/Scripts/test262-import --help for details.

--src and --remote are mutually exclusive. A local source must be a clean Git checkout containing test/ and harness/ directories.

Both tools require Python 3 and PyYAML (pip3 install pyyaml). They rely on webkitcorepy and webkitpy, which live in the tree under Tools/Scripts, so no other setup is needed.

The runner and importer live in Tools/Scripts/test262/ (runner.py and importer.py); the top-level test262-runner and test262-import scripts are thin wrappers around them.

The test262 tree is registered with test-webkitpy:

./Tools/Scripts/test-webkitpy test262

Or run a single module directly:

cd Tools/Scripts/test262
python3 -m unittest runner_unittest importer_unittest