How to Print Slowest Tests in Vitest?

[sumitcr7]

I want to print the slowest tests in Vitest. Is there any built-in way to do this? If not, can this be achieved using a custom reporter? If anyone has implemented this or has suggestions, please share.

[hi-ogawa]

Not available as builtin, but a custom reporter can do something like this. https://stackblitz.com/edit/vitest-dev-vitest-as4c3dmw?file=vite.config.ts

export default defineConfig({
  test: {
    reporters: [
      'default',
      {
        onTestRunEnd(testModules, unhandledErrors, reason) {
          const tests = testModules.flatMap((m) => [...m.children.allTests()]);
          tests.sort(
            (x, y) => x.diagnostic()?.duration! - y.diagnostic()?.duration!
          );
          tests.reverse();
          console.log(
            Object.fromEntries(
              tests.map((t) => [
                `${t.module.moduleId} | ${t.fullName}`,
                t.diagnostic()?.duration,
              ])
            )
          );
        },
      },
    ],
  },
});

{
  '/home/projects/vitest-dev-vitest-as4c3dmw/test/suite.test.ts | suite name > snapshot': 0.9900010000001203,
  '/home/projects/vitest-dev-vitest-as4c3dmw/test/basic.test.ts | Math.sqrt()': 0.7350009999936447,
  '/home/projects/vitest-dev-vitest-as4c3dmw/test/suite.test.ts | suite name > foo': 0.5550000000000637,
  '/home/projects/vitest-dev-vitest-as4c3dmw/test/basic.test.ts | JSON': 0.3999999999650754,
  '/home/projects/vitest-dev-vitest-as4c3dmw/test/suite.test.ts | suite name > bar': 0.24000099999989288,
  '/home/projects/vitest-dev-vitest-as4c3dmw/test/basic.test.ts | Squared': 0.15999999997438863
}

Also test duration reporting is sometimes a part of CI platform integration. For example, I remember circleci tracks test durations over the time if you upload Vitest's junit reporter output. https://circleci.com/docs/insights-tests/#slowest-tests