Addon-vitest: Fix wrong test count in telemetry

[JReinhold]

Closes #31493

What I did

1. stopped collecting selectedStoryCount, as it was both confusing and not that useful
2. Flushed all pending test case results when test runs finishes. Let me explain:

Test case results continuously come in from Vitest in a steady stream. We throttle the handling of them, because otherwise it consistently chokes our websocket connection for some reason. (this is very unfortunate, because seeing the test ran count go brrr is really great UX, but for some reason it's too many events for our channel). The problem here, was that when all tests completed we would emit TEST_RUN_COMPLETED immediately, even though there were still unhandled test case results left because of the throttled handling. This would result in the unhandled results not being part of the telemetry being emitted.

Now, when Vitest calls the onTestRunEnd lifecycle hook - which happens just before runTestSpecifications finishes and thus our test run - we flush the throttle function, meaning that we force handle any test case results that are left. Then the test run actually finishes, and we send the telemetry event will all test case results.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

1. In scripts run yarn jiti ./event-log-collector.ts
2. Start the UI Storybook or a sandbox with the environment variable STORYBOOK_TELEMETRY_URL="http://localhost:6007/event-log" yarn storybook
3. Run local tests with a11y from within the testing widget
4. Visit http://localhost:6007/event-log and check that the last event has the same number of tests as those reported in the testing widget

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

Greptile Summary

Fixed incorrect test count reporting in telemetry data for the Vitest addon by ensuring all test results are properly processed before sending completion events.

• Added flush() call in code/addons/vitest/src/node/test-manager.ts to process pending throttled test results before emitting completion event
• Removed confusing selectedStoryCount metric from telemetry data in code/addons/vitest/src/preset.ts
• Maintained 500ms throttling of test case results to prevent websocket overload

[greptile-apps]

LGTM

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☁️ Nx Cloud last updated this comment at 2025-05-16 19:36:10 UTC