Smoke Tests

Running Smoke Tests

Smoke tests live in test/smoke/ and drive a full VS Code instance (Electron, web, or remote) through end-to-end user flows.

Scripts

• npm run smoketest — compiles the smoke tests first (test/smoke), then runs them.
• npm run smoketest-no-compile — runs the already-compiled smoke tests. CI uses this after an explicit compile step.

Both forward extra arguments after -- to the runner (test/smoke/test/index.js).

Common options

# Run everything (Electron, from source)
npm run smoketest

# Run only a subset of suites by name, with tracing (replace <suite name> with your suite, e.g. "Agents Window")
npm run smoketest -- -g "<suite name>" --tracing

# Run against a packaged build (CI style)
npm run smoketest-no-compile -- --tracing --build "/path/to/VSCode-darwin-arm64/Code - OSS.app"

The -g pattern matches against test/suite titles. For example, -g "Agents Window" matches all three Agents Window suites (Agents Window, Agents Window (local AgentHost), and Agents Window (local AgentHost, SDK sandbox)); use whatever substring identifies the suite(s) you care about.

The runner exits non-zero if any test fails, so a 0 exit code means every selected test passed.

Temporarily looping a suite to hunt flaky CI tests

When a smoke test fails intermittently only in CI, a useful technique is to temporarily run the suspect suite many times in a row and fail on the first failure. This reproduces the flake under the real CI environment and captures its traces/screenshots, instead of waiting for it to recur naturally across unrelated PRs.

This is a debugging aid, not a permanent CI fixture:

• Add it on a throwaway branch, push, and let CI run it. Iterate until you reproduce (and then fix) the flake.
• Remove the loop before merging — leaving it in would add ~an hour per platform to every run.
• It is not specific to any one suite. Point the -g filter at whichever suite you are investigating (the examples below use "Agents Window", but substitute your own).

Where to add it

Drop the loop next to the existing Electron smoke step, gated on the same condition, in the test step(s) for the platform(s) where the flake reproduces:

GitHub PR workflows (run from source, no --build):

• .github/workflows/pr-linux-test.yml (bash; sets DISPLAY: ":10")
• .github/workflows/pr-darwin-test.yml (bash; no DISPLAY)
• .github/workflows/pr-win32-test.yml (PowerShell)

Azure DevOps test steps (run against the packaged build via --build):

• build/azure-pipelines/linux/steps/product-build-linux-test.yml
• build/azure-pipelines/darwin/steps/product-build-darwin-test.yml
• build/azure-pipelines/win32/steps/product-build-win32-test.yml

Shape

Loop N iterations (e.g. 20) and abort on the first failing run. Give it a generous timeout — N sequential runs of a ~3-minute suite can take roughly an hour.

Bash (Linux/macOS):

# TEMPORARY: loop the suite to reproduce a flaky failure. Remove before merge.
# Replace <suite name> with the suite you're investigating (e.g. "Agents Window").
- name: 🧪 Smoke test flakiness probe (TEMPORARY)
  if: ${{ inputs.electron_tests }}
  timeout-minutes: 60
  run: |
    for i in $(seq 1 20); do
      echo "::group::Smoke probe run $i/20"
      npm run smoketest-no-compile -- --tracing -g "<suite name>" || { echo "::error::Smoke test failed on run $i/20"; exit 1; }
      echo "::endgroup::"
    done

PowerShell (Windows) checks $LASTEXITCODE after each run and exit 1 on failure. The AzDO variants use set -e (bash) / $LASTEXITCODE (pwsh) for fail-fast and append --build "<packaged app path>".

Why fail-fast

The loop is a probe: the first failure is the signal. Stopping immediately preserves the failing run's traces/screenshots (under the logs artifact) and avoids burning ~an hour of agent time finishing a run that has already proven flaky.

Debugging CI smoke failures

Both CI systems publish the smoke runner's per-platform logs (the .build/logs directory) as a downloadable artifact. The artifact's internal layout is identical on both — only the artifact name and the download tool differ.

Downloading the logs artifact

GitHub Actions

The GitHub PR workflows upload the artifact as logs-<os>-<arch>-<suite>-<attempt>, where <os> is linux / macos / windows, <suite> is electron / browser / remote, and <attempt> is the run attempt (e.g. logs-macos-arm64-electron-1).

The run id is the number in the run/job URL — for …/actions/runs/<run-id>/job/<job-id> use <run-id>. Download with the gh CLI:

# A specific artifact into ./logs
gh run download <run-id> -n logs-<os>-<arch>-<suite>-<attempt> -D ./logs

# Or every artifact from the run
gh run download <run-id>

gh run view <run-id> lists the run's jobs/artifacts; the run summary page in the browser also has an Artifacts section at the bottom.

Azure DevOps

The artifact name depends on which pipeline produced it:

• Product build (product-build-<os>.yml): logs-<os>-<arch>-<attempt> — no suite segment, e.g. logs-macos-arm64-1.
• Suite-split CI build (product-build-<os>-ci.yml): logs-<os>-<arch>-<suite>-<attempt> — the <suite> segment is lower(VSCODE_TEST_SUITE) (e.g. electron), so e.g. logs-macos-arm64-electron-1 (same shape as GitHub).

<os> is linux / macos / windows, <arch> is x64 / arm64, and <attempt> is $(System.JobAttempt). Download with the Azure CLI:

az pipelines runs artifact download \
  --org <ORG_URL> --project <PROJECT_NAME> \
  --run-id <BUILD_ID> --artifact-name <artifact-name> \
  --path ./logs

For the VS Code build that is --org https://dev.azure.com/monacotools --project Monaco; see the azure-pipelines skill for finding the <BUILD_ID>.

Inside the artifact

Under smoke-tests-<suite>/ (smoke-tests-electron/, smoke-tests-browser/, or smoke-tests-remote/, matching the suite that ran):

• smoke-test-runner.log — the mocha driver output.
• <N>_suite_<Suite_Name>/window2/exthost/<extension>/…log — per-suite extension-host logs (e.g. <publisher>.<name>/<Display Name>.log). Many diagnostics are gated behind a setting the suite enables in its before hook, so check the suite's setup if an expected log line is missing.
• <N>_suite_<Suite_Name>/playwright-screenshot-*.png — last-frame screenshot captured when a test fails (only when the suite ran with --tracing).

<Suite_Name> is the mocha suite title with non-word characters replaced by _. See also the code-oss-logs skill.

Distinction from other test types

• Unit tests (.test.ts) → scripts/test.sh / runTests tool (see the unit-tests skill).
• Integration tests (.integrationTest.ts + extension tests) → scripts/test-integration.sh (see the integration-tests skill).
• Smoke tests (test/smoke/) → npm run smoketest — full end-to-end UI flows.