unit-test: browser-mode runs stall ("iframe did not become ready") when a Docker container starts alongside #34390

Command

test

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

With "browsers": ["chromiumHeadless"] and @vitest/browser-playwright, ng test stalls in roughly 4 runs of 10 when a Docker container starts while the tests start up. That is what happens when another package of a workspace runs integration tests with Testcontainers at the same time. A few test iframes load Vitest's runtime and never request the Angular test setup (init-testbed.js) or their spec chunks; after 60 s the run fails.

On a fresh ng new app with six generated components:

The last row (on Vitest 5.0.4; the others on 5.0.4 and 5.0.5 alike) is why I am filing it here rather than with Vitest. Ruled out on the same machine: CPU load (all 16 cores busy), synchronous disk writes, touching a source file mid-run, the image or a published port (alpine sleep is enough), and the headless shell itself (the full Chromium build stalls too, less often). Chromium logs no failed request and no console error, and a page opening ~1000 fresh connections to localhost while a container starts loses none.

With DEBUG=vitest:browser:*, all seven sessions connect to the tester API at the same moment, then only two send their first command (__vitest_viewport); the other five stay silent until the 60 s timeout. A Vite request trace (DEBUG=vite:time) of a stalled run shows those five iframes fetched index, plugins and rolldown-runtime from the optimized deps and nothing after; a passing run goes on to init-compiler.js, init-testbed.js, the Angular deps and the spec files.

It may be the same family as vitest-dev/vitest#11171 (a rejected import inside the tester iframe never fires iframe.onerror, so the orchestrator waits until the timeout), closed there for want of a reproduction.

Minimal Reproduction

npx @angular/cli@22.2.3 new ng-docker-stall --defaults --skip-git --ssr=false --style=css
cd ng-docker-stall
for c in alpha bravo charlie delta echo foxtrot; do npx ng g c "$c"; done
npm install -D --save-exact vitest@5.0.5 @vitest/browser-playwright@5.0.5 playwright@1.64.1
npx playwright install --only-shell chromium
npx ng config projects.ng-docker-stall.architect.test.options.browsers '["chromiumHeadless"]'
npx ng test    # passes

Then, with Docker running, this script, ./stall.sh 10:

#!/bin/sh
# Runs `ng test` several times while a Docker container starts beside it, and
# counts the runs whose test iframes stall.
runs=${1:-5}
stalled=0
for i in $(seq 1 "$runs"); do
  (id=$(docker run -d alpine:3 sleep 8); sleep 9; docker rm -f "$id" > /dev/null) &
  if npx ng test 2>&1 | grep -q 'did not become ready'; then
    stalled=$((stalled + 1))
    echo "run $i: stalled"
  else
    echo "run $i: passed"
  fi
  wait
done
echo "$stalled of $runs runs stalled"

Expected: every run passes, as without the container. Actual: some runs stall and fail after 60 s.

Exception or Error

⎯⎯⎯⎯⎯⎯ Unhandled Error ⎯⎯⎯⎯⎯⎯⎯
Error: Failed to run the test /…/ng-docker-stall/src/app/echo/echo.spec.ts.
 ❯ process.processTicksAndRejections node:internal/process/task_queues:104:5
Caused by: Error: The iframe "__vitest_all__" did not become ready within 60000ms. The tester likely failed to initialize, check the browser console for errors.
 ❯ ../../../../../../../__vitest_browser__/orchestrator-C2U7TVD1.js:198:28

 Test Files   (7)
      Tests  no tests
     Errors  1 error
   Duration  61.05s

Your Environment

Angular CLI       : 22.2.3
Angular           : 22.2.3
Node.js           : 24.22.0
Package Manager   : npm 11.19.1
Operating System  : linux x64

┌───────────────────────────┬───────────────────┬───────────────────┐
│ Package                   │ Installed Version │ Requested Version │
├───────────────────────────┼───────────────────┼───────────────────┤
│ @angular/build            │ 22.2.3            │ ^22.2.3           │
│ @angular/cli              │ 22.2.3            │ ^22.2.3           │
│ @angular/common           │ 22.2.3            │ ^22.2.0           │
│ @angular/compiler         │ 22.2.3            │ ^22.2.0           │
│ @angular/compiler-cli     │ 22.2.3            │ ^22.2.0           │
│ @angular/core             │ 22.2.3            │ ^22.2.0           │
│ @angular/forms            │ 22.2.3            │ ^22.2.0           │
│ @angular/platform-browser │ 22.2.3            │ ^22.2.0           │
│ @angular/router           │ 22.2.3            │ ^22.2.0           │
│ rxjs                      │ 7.8.2             │ ~7.8.0            │
│ typescript                │ 6.0.3             │ ~6.0.2            │
│ vitest                    │ 5.0.5             │ 5.0.5             │
└───────────────────────────┴───────────────────┴───────────────────┘

Anything else relevant?

• @vitest/browser-playwright 5.0.5, playwright 1.64.1 (Chrome Headless Shell 156.0.8078.4). Only Chromium was tried.
• Ubuntu 26.04.1 LTS, Linux 7.0.0, Docker 29.9.1 (native engine, cgroup v2).
• The workaround we use is running the workspace's packages one after another, so no container starts while the browser tests run.