Description

Close: #7914

Hi Team 👋

As described in #7914 (comment), I understand that #7914 happens because mergeConfig merges array in config object instead of overriding it.

As mentioned in docs, vitest config root's include option has ['**/*.{test,spec}.?(c|m)[jt]s?(x)'] as default value, and config which is calculated per browser instance configuration will be like below:

// input vitest.config.ts

export default defineConfig({
  test: {
    browser: {
      enabled: true,
      provider: 'playwright',

      instances: [
        // Run all tests with Chromium, it's stable
        { browser: "chromium" },

        // Firefox is flaky, run just one test 
        { browser: "firefox", include: ["test/something-simple.test.ts"] },
      ],
    },
    // include: ['**/*.{test,spec}.?(c|m)[jt]s?(x)'] as default value
  },
});

// output config for chromium
export default defineConfig({
  test: {
    ...config,
    include: ['**/*.{test,spec}.?(c|m)[jt]s?(x)']
});

// output config for firefox
export default defineConfig({
  test: {
    ...config,
    include: ['**/*.{test,spec}.?(c|m)[jt]s?(x)', "test/something-simple.test.ts"]
});

and so, '**/*.{test,spec}.?(c|m)[jt]s?(x)' pattern in firefox's config will match test files which should be ignored by config.browsers.instances[firefox].include.

I thought vitest user expect include config in deeper will be prioritized than the root that, so I fixed this issue by ignoreing project root's include value if config.browser.instances[].include is specified.

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