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…ghten their assertions Every test used to open its own tab, serially. A tab is a renderer process that Chrome creates one at a time (~100-165ms each), which is what made this file take 17-22s on the Linux lanes. Page-level tests now borrow one of two long-lived tabs and navigate it (~20-30ms); only lifecycle/configuration tests open their own tabs, at most four at a time; the three process-level tests read different parts of one shared child bun process with a Chrome of its own. The test that observes the whole tab list runs alone after the concurrent group and orders itself with CDP round trips instead of a 200ms sleep. The animation test waits for the animation to actually be running before clicking, which removes a race that fired frequently under load. Assertions now compare whole error shapes (name/code/message), whole evaluate() results, event payloads and console calls with one toEqual each, check the PNG signature and IHDR dimensions, compare the screenshot encodings byte for byte, and verify that closed views' tabs disappear from Target.getTargets. Also covers backend.path, the Page.navigate errorText path, every scrollTo block value, empty selectors and two more constructor validation cases.
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WalkthroughChangesThe Chrome WebView test suite adds capability gating, pooled page scheduling, shared subprocess coverage, reusable assertions, and broader validation for lifecycle, evaluation, screenshots, CDP, input, navigation, viewport, console, and cancellation behavior. Chrome WebView test suite
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Inline comments:
In `@test/js/bun/webview/webview-chrome.test.ts`:
- Around line 421-426: Update the child-process result flow around readFileSync
and the returned chromeArgv value to tolerate a missing argv.txt, returning an
appropriate empty/default argument list when the file does not exist while
preserving the captured stdout, stderr, and exitCode so child diagnostics remain
visible.
- Around line 360-364: Change the “chrome: console option validates” case from
it to plain test so its synchronous option validation runs even when Chrome is
unavailable, matching the neighboring test.each validation block.
- Around line 204-212: Update the catch/finally flow around page.close,
newPooledPage, and idlePages so replacement-page creation cannot overwrite the
original error and a closed page is never returned to the pool. Track the
replacement in a separate local, handle replacement failure without masking the
caught error, and have finally enqueue only a live replacement page when one was
successfully created.
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test/js/bun/webview/webview-chrome.test.ts
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Status: ready for review; CI on 2f265f6 is green for this file on every lane, the one red test ( What the change buys, measured two ways:
Lanes without Chrome still see every Chrome test as todo. Coverage mapping and methodology are in the description. |
…ion into the table, tolerate a missing argv.txt A pooled tab whose test failed is now simply closed and the next borrower opens a fresh one, so the original failure is what gets reported even if Chrome is in a bad state. The console option validation runs without Chrome like the other constructor validation cases. If the launcher script never ran, the child's own stderr and exit code are what the tests show rather than an ENOENT.
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Updated 12:13 PM PT - Aug 15th, 2026
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robobun
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I reviewed this PR and the bug hunting pass found no issues; the pool-recovery concern from the earlier commit is fixed in 37aecb7. Because this is a ~1200-line rewrite that introduces new test-concurrency infrastructure (the lanes semaphore, tab pool with failure-retirement, one shared child split across three tests, ordering-based assertions replacing sleeps), a human look at the design would still be worthwhile.
What was reviewed:
onPooledPagefailure path — a failed test's tab is closed and never re-pooled; the next borrower creates a fresh one, so the original error propagates unchanged.lanes()semaphore — thefinallyhands the slot to the next waiter or decrementsbusy; no path leaks a slot.observeSharedChild—tempDirlifetime spans the awaited spawn, argv.txt is read only if it exists, and stdout/stderr/exited are drained concurrently.- The final
closeAlltest is placed last (afteritAlone) so it can't kill the shared Chrome under the concurrent group; theitAloneattach-chain test refills the pool if earlier failures emptied it.
Extended reasoning...
Overview
This PR rewrites test/js/bun/webview/webview-chrome.test.ts (the only file touched) to cut wall-clock from 17-22s to ~4-5s per CI lane. It replaces ~48 serial per-test tabs with a 2-tab pool (itOnPage), a bounded lane for own-tab tests (it, cap 4), and one lazily-spawned child bun process shared across three process-level tests (itInChild). It also tightens most assertions from regex/toContain to exact toEqual on error shapes, adds a 14-case constructor-validation test.each table, and replaces the attach-chain test's 200ms sleep with a CDP ordering argument. No runtime code is touched.
Security risks
None. Test-only; the launcher shell script embeds chromePath (from local filesystem discovery) via single-quoted interpolation, and the child script embeds the temp dir path via JSON.stringify. No network hosts are contacted (data: URLs and one http://127.0.0.1:1/ that Chrome rejects as ERR_UNSAFE_PORT before opening a socket).
Level of scrutiny
Medium-high. Although test-only, this introduces bespoke concurrency machinery (lanes, pool-with-retirement, shared-child memoization) whose correctness affects whether failures are reported cleanly vs. cascade. The PR description documents pid/shm exhaustion measurements that motivated the caps, and acknowledges a residual rare flake in the animation test under load-average >200 (same window as main, root-cause fix in #35173). The design choices — pool size 2, tab lane 4, itAlone placed after the concurrent group, closeAll last — are all load-bearing and worth a maintainer's eye.
Other factors
All three CodeRabbit findings and my own earlier inline comment (closed tab re-entering the pool) were addressed in 37aecb7. The one CI failure in build #98198 (test-http-chunk-problem.js ASAN) is unrelated. The PR description lists four other open PRs touching this file that will need rebasing on whichever lands first. Given the scope and the number of interacting design decisions, deferring to a human reviewer rather than auto-approving.
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Problem
test/js/bun/webview/webview-chrome.test.tstakes 17-22s on every Linux lane that has Chrome (24.5s on alpine aarch64, 22.2s on the x64 ASAN lane in build #97275); it is inparallel-allowlist.json'sexcludeFilesbecause of that.new WebView+ firstnavigate()on 12 cores and ~165ms on 4, and the same per-tab cost whether 1 or 16 are opened at once. Navigating a tab that already exists costs ~20-30ms, anevaluate()/click()~2ms, and launching a bun child with its own Chrome (four tests did this) ~0.4s.urlchecked withtoContain, subprocess stderr checked withnot.toContain("ERROR:"), errors matched with regexes,reload()checked viaDate.now()inequality, the "circular reference" test actually exercised a SyntaxError, nothing verified that a closed view's tab goes away, and the attach-chain test waited on a 200mssetTimeout.Fix
itOnPage) borrow one of two long-lived tabs created inbeforeAlland navigate it to their HTML; the tab is handed back afterwards. A failed test's tab is closed instead, and the next borrower opens a fresh one, so an operation left pending by a failure can't poison the next test and the original failure is what gets reported (checked by temporarily injecting two failing pooled tests). Two tabs measured as fast as four or eight, since tab work funnels through Chrome's browser process.it) still open their own tabs, at most four at a time. The three process-level tests (backend.path/argv,console: globalThis.console,closeAll()) each assert on a different part of one shared child bun process, launched on first use so it overlaps the tab tests. The caps are in the file rather than left to--max-concurrencybecause Chrome is ~135 threads plus ~10 per tab and a child is ~145 more; two extra Chromes at once already peaked near this container's 512-pid limit, 40 tabs at once aborted Chrome on it, and 20 tabs taking screenshots used most of its 64MB/dev/shm. Peak during a run is now ~400 pids.test.todowhenfindChrome()finds nothing or on the macOS < 15 CI boxes; the ungated tests are still only option validation (now a 14-case table, including theconsoleoption cases that used to be gated for no reason) plus thecloseAllstatic check (now last, since it kills the shared Chrome; before, it did so mid-file). Lanes without Chrome run the file in ~0s as before: 15 pass, 43 todo, nothing spawned.name/code/message) compared exactly via athrown()/rejection()helper wherever the text is bun's, regexes kept only for Chrome-produced text;evaluate()results, theNetwork.requestWillBeSentpayload, console calls, history walks and the scrollTo table asserted with onetoEqualeach; PNG checked by full signature plus IHDR dimensions (also afterresize()); buffer/base64/shmem screenshots compared byte for byte with the Blob, shmem object checked exactly and read back from/dev/shmon Linux;close()tests check the tab disappears fromTarget.getTargetsand that the other view keeps working;reload()verified by a mutation disappearing; the large-payload test round-trips 100KB both ways; the child's stderr must be exactly the one forwardedconsole.errorline, which is a stricter form of the old "stderr defaults to ignore" test.backend.pathactually selecting the executable and the real argv order Chrome receives (a launcher script records it), thePage.navigateerrorText rejection, all fivescrollToblock values and its timeout, empty selectors,argvnot being an array,width: 0, the evaluate slot guard,close()idempotence and the closed-view errors, and the statement-vs-expression contract ofevaluate(). Every behaviour the old 52 tests checked still has a test; 58 tests now (the four validation tests became a 14-case table, the four screenshot tests became two, the two url/title tests one).toMatchObjectwith asymmetric matchers on objects the test reuses, since it mutates the received object (expect.any/toMatchObjectmutates the object #3521, fix in expect: stop toMatchObject/toMatchSnapshot from mutating the received object #35452).Verification (Google Chrome 151.0.7922.137 from
/usr/bin/google-chrome-stable; the container runs as root, soBUN_CHROME_PATHpointed at a two-lineshwrapper that execs it with--no-sandbox; the host was heavily loaded during all measurements, load average 140-195, so individual numbers are noisy):bun bd test(debug+ASAN), 12 CPUsbun bd test, pinned to 4 CPUs (taskset, CI lanes are 4 vCPU)bun test, 12 CPUsbun test, pinned to 4 CPUsThe table was taken just before the animation-wait change, which only adds ~0.1s to one overlapped test. About 4.4s of every debug number is the debug binary's fixed startup for this file (a run with Chrome hidden, where everything is todo, takes 4.4-4.5s). Stability of the final version: 12 consecutive release runs (2.8-5.6s) and 4 debug runs (6.3-10.0s) all green under that load, plus the whole
test/js/bun/webview/directory in one process, and a run with Chrome hidden.What CI itself measured, from the Buildkite per-line timestamps in the job logs (the file runs as its own
bun testprocess, so the gap before the first progress dot is bun's startup plus whatever has to happen before the first test completes):beforeAll: Chrome's first launch on the agent + 2 tabs)So on a CI agent the first launch of Chrome costs anywhere from 2.5s to 18s depending on the agent (the file is among the first to run, on a cold box), and that is most of the 17-24s the slow-test report was seeing; it is the same before and after, and nothing in a test file can avoid paying it once. The part this PR controls went from 4.7-8.3s to ~4.5s per lane, and the file launches two Chromes per run instead of five. (The main run's alpine aarch64 log also shows the runner's temp-dir cleanup failing with ENOTEMPTY right after this file, which is the leaked
--user-data-dirhanded off above.)Related PRs that also touch this file and will need a small rebase on whichever lands second: #39064, #39075, #35173, #29953. Bugs in the backend found while writing this, handed off separately: the viewport coming out 87px short of
heightwith full Chrome (the pool pins its tabs to 300x300 withresize()because of it), failed navigations never callingonNavigationFailed, the attach-chain tab leak (#39075), the console callback'snull/NaNmapping (#39064), and the temp--user-data-dirnever being deleted (386 of them, 756MB, after this session's runs).Background
--remote-debugging-pipe); everynew Bun.WebView()whosenavigate()is awaited becomes a tab viaTarget.createTarget, with its own CDP session, so views are independent of each other and can be driven concurrently. Options such aspath,argvand stdio only matter for the first spawn in a process, which is why those tests need a child process.Target.getTargets/Target.getTargetInfo, sent through any live view'scdp(), list Chrome's tabs;close()sendsTarget.closeTargetwithout waiting for the reply, so the tests poll the list until the tab is gone (about 10ms).bun testruns consecutivetest.concurrenttests as one group (up to--max-concurrency, default 20); a plaintestafter them runs by itself once the group has drained, which is what the tab-list test and the finalcloseAllrely on. A concurrent test's duration includes any time it spends waiting for a tab.click(selector)resolves only after the element's bounding box has been identical on two consecutive samples, which is what the animation test exercises.Measurements behind the design (release build, this host)