openworkers-conformance

One suite of guest JavaScript, run unchanged on every OpenWorkers runtime, to measure what each backend actually implements.

A low score is a result, not a failure: the suite is written against the WinterTC (TC55) Minimum Common API and the specs it points at, never against what a runtime happens to do. Guest assertions never set the exit code, so the run stays usable while the runtimes are incomplete.

Layout

tests/ holds plain classic scripts. Each declares its tests with test('name', fn) at column 0, and asserts with the helpers the harness injects (assert, assertEqual, assertType, assertArrayEqual, assertThrows, assertRejects). Nothing in a test file is backend-specific.

area	file	tests
crypto	js/crypto/crypto.js	30
encoding	js/encoding/base64.js	20
encoding	js/encoding/text.js	35
globals	js/globals/abort.js	24
globals	js/globals/blob.js	26
globals	js/globals/microtasks.js	10
globals	js/globals/misc.js	16
globals	js/globals/structured-clone.js	17
globals	js/globals/timers.js	16
headers	js/headers/headers.js	28
request	js/request/request.js	29
response	js/response/response.js	38
streams	js/streams/streams.js	25
url	js/url/search-params.js	35
url	js/url/url.js	33
wintercg	wintercg/minimum-common-api.js	66
	total	448

Every file runs in a fresh worker, and every test runs under a 2s deadline, so one missing global costs its own line and nothing else. The denominator comes from the source, not from the run: a backend that cannot parse a file still scores 0/N against the same N as the others.

Running

cargo run --release --features v8 --bin conformance
cargo run --release --features boa --bin conformance -- --verbose
cargo run --release --features quickjs --bin conformance -- --filter url
cargo run --release --features jsc --bin conformance -- --json

One backend per build, like the rest of the workspace. --verbose lists every failing test, --json emits the whole run, --filter selects by path.

Scoreboard

Measured 2026-08-21, one commit per runtime, all against openworkers-core v0.15.0.

area	v8	jsc	quickjs	boa
crypto (30)	30	23	21	10
encoding (55)	45	33	44	47
globals (109)	86	37	43	80
headers (28)	23	24	24	24
request (29)	22	19	16	20
response (38)	28	27	21	30
streams (25)	13	12	11	13
url (68)	68	66	66	66
wintercg (66)	38	27	24	29
total (448)	353	268	270	319
	78%	59%	60%	71%

Branch names lag the code: every one of these builds against core v0.15.0.

backend	branch	commit
v8	main	fe3fb23
jsc	feat/core-0.14	2df2560
quickjs	feat/core-0.14	ed14afe
boa	feat/core-0.14	9dec1ee
wasm	feat/core-0.14-wasmtime-bump	c97afa3

What the numbers say

77 of the 448 tests fail on all four backends, so most of the gap is the platform's, not any one engine's.

• v8 is the only backend with a complete URL and a complete crypto, 68/68 and 30/30. Its subtle covers the six digests, AES-GCM round trips, raw HMAC and AES key import and export, and ECDSA key generation. jsc and quickjs stop after digest and HMAC; boa has no subtle.digest at all, which is most of the distance between its 10/30 and everyone else.
• jsc and quickjs miss URL.canParse and URL.parse and nothing else in url.js; boa takes url.js whole and loses its two points on URLSearchParams. All three back URL with the url crate.
• boa is 34 behind v8 (319 against 353) on the strength of boa_wintertc, while being the weakest on crypto by far.
• No backend exposes Event or EventTarget, so the DOM event core of the Minimum Common API is missing everywhere, and with it CustomEvent, ErrorEvent, MessageEvent, PromiseRejectionEvent and AbortSignal.any. AbortController exists on v8 (8/8) and boa (6/8) only.
• No backend sorts Headers iteration by name, none rejects an invalid name or a value with a newline, and none trims whitespace around a value. v8 alone also fails to comma-join Set-Cookie in get.
• No backend sets Content-Type from the body on Request or Response, so neither a string nor a URLSearchParams arrives with its type, and none enforces the status rules (a body with 204 or 304, a status below 200 or above 599).
• Streams stop at ReadableStream: WritableStream, TransformStream, the queuing strategies, TextEncoderStream/TextDecoderStream, CompressionStream, pipeTo and ReadableStream.from are missing on all four, tee exists on v8 and boa only, and no backend makes a stream async-iterable.
• structuredClone, Blob and File exist on v8 and boa only, and multipart/form-data parses on v8 alone.
• performance exists on v8 and quickjs, and only quickjs carries timeOrigin; self exists on v8 and boa.

Streaming battery

The guest suite asks what a script can observe about itself. It cannot see a body that does not arrive all at once, because only the host is on the other end of the channel. src/streaming/ is that second measurement, and STREAMING.md holds its matrix.

cargo run --release --features v8 --bin streaming
cargo run --release --features jsc --bin streaming -- --filter backpressure
cargo run --release --features wasm --bin streaming -- --json

25 probes on the JavaScript backends, 4 on wasm, each in its own thread with its own deadline, so a runtime that deadlocks mid-stream costs one line and gets reported as hangs rather than taking the run with it.

Backends

One cargo feature per backend, mutually exclusive, the same pattern as openworkers-task-executor.

wasm builds and reports a skip: that runtime executes wasm components, not JavaScript, so this suite has nothing to say about it. Reporting 0/448 there would be a lie, not a measurement.

nova has no feature at all. nova_vm 1.0 pulls temporal_rs 0.1.2, written against icu_calendar 2.1, while v8 152 pulls temporal_capi 0.2.3+, which wants 2.2. One lockfile cannot hold both, and this crate needs v8.

SSR oracle

examples/ssr_oracle.rs and fixtures/sveltekit-app/ are a separate, complementary measurement: 17 scenarios of a real SvelteKit app, recorded on v8 and diffed byte for byte by the other runtimes.

cargo run --release --features v8 --example ssr_oracle -- --check