Browser mode tests slow down all tests in Github Actions

[janpe]

Describe the bug

I'm in the process of migrating some tests in a project to run in browser mode. I currently have 507 tests and I started by migrating 3 of those to browser mode. I have made the following changes to my config:

Before

test: {
    globals: true,
    environment: 'jsdom',
    setupFiles: ['./vitest.setup.js'],
    watch: false,
}

After

test: {
    globals: true,
    watch: false,
    projects: [
      {
        extends: true,
        test: {
          name: 'jsdom',
          environment: 'jsdom',
          setupFiles: ['./vitest.setup.js'],
          include: defaultInclude,
          exclude: browserInclude,
        },
      },
      {
        extends: true,
        test: {
          name: 'browser',
          browser: {
            provider: playwright(),
            enabled: true,
            headless: true,
            instances: [{ browser: 'chromium' }],
          },
          include: browserInclude,
        },
      },
    ],
}

Making these changes almost doubles the time it takes to run all the tests even though the 3 browser tests run quite quickly. The browser tests are run initially and after this the jsdom tests run but much slower than usual. Locally on my computer I cannot see a significant change between these cases.

Before
Duration 284.83s (transform 3.58s, setup 121.86s, import 73.16s, tests 23.10s, environment 39.53s)

After
Duration 473.52s (transform 5.90s, setup 203.70s, import 118.68s, tests 45.82s, environment 64.73s)

I have seen some similar discussion here: #6223

Reproduction

I currently have no reproduction since the project is private and this needs a CI setup to be reproduced.

System Info

Only happens on Github Actions

Used Package Manager

yarn

Validations

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[github-actions]

Hello @janpe. Please provide a minimal reproduction using a GitHub repository or StackBlitz (you can also use examples). Issues marked with needs reproduction will be closed if they have no activity within 3 days.

[janpe]

@sheremet-va I created a repro repo but it seems that this is difficult to reproduce with a small number of simple tests which does not match what would happen in a big real life project. Is there any way to get output about each step (transform, setup, import, tests, environment) for each test/project?

The repo can be found here: https://github.com/janpe/vitest-slow-issue

There are two branches: main has jsdom tests and the other one has one of the tests migrated to a browser test. There is a Github action to run the tests in CI.

[sheremet-va]

Is there any way to get output about each step (transform, setup, import, tests, environment) for each test/project?

You can try open telemetry: https://vitest.dev/config/experimental.html#experimental-opentelemetry