Obsolete test snapshots do not cause test run to fail in CI environments

[Arskah]

Describe the bug

Filed as a bug based on the discussion here: #7882 (comment)

When running Vitest in CI pipelines, obsolete snapshots do not cause failures.

Reproduction

Arskah/vitest-obsolete-snapshot#3

System Info

System:
    OS: macOS 15.4.1
    CPU: (10) arm64 Apple M2 Pro
    Memory: 7.24 GB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 22.14.0 - ~/.asdf/installs/nodejs/22.14.0/bin/node
    Yarn: 1.22.22 - ~/.asdf/installs/nodejs/22.14.0/bin/yarn
    npm: 10.9.2 - ~/.asdf/installs/nodejs/22.14.0/bin/npm
    pnpm: 9.15.4 - ~/.asdf/installs/nodejs/22.14.0/bin/pnpm
  Browsers:
    Brave Browser: 135.1.77.95
    Chrome: 135.0.7049.116
    Safari: 18.4
  npmPackages:
    vitest: 3.1.3 => 3.1.3

Used Package Manager

npm

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.

[hi-ogawa]

It's rough but user land solution is possible using custom reporter https://stackblitz.com/edit/vitest-dev-vitest-ap23doa8?file=vite.config.ts

import { defineConfig } from 'vitest/config';
import type { Reporter, Vitest } from 'vitest/node';

export default defineConfig({
  test: {
    reporters: ['default', rejectObsoleteSnapshot()],
  },
});

function rejectObsoleteSnapshot(): Reporter {
  let vitest: Vitest;

  return {
    onInit(vitest_) {
      vitest = vitest_;
    },
    onTestRunEnd() {
      if (
        vitest.snapshot.options.updateSnapshot === 'none' &&
        vitest.snapshot.summary.unchecked
      ) {
        throw new Error(
          'Obsolete snapshots found: ' +
            JSON.stringify(vitest.snapshot.summary.uncheckedKeysByFile, null, 2)
        );
      }
    },
  };
}

$ CI=true vitest

 RUN  v3.1.3 /home/projects/vitest-dev-vitest-ap23doa8

 ✓ test/suite.test.ts (3 tests) 2ms
 ✓ test/basic.test.ts (3 tests) 3ms

  Snapshots  1 obsolete
             ↳ test/suite.test.ts
               · suite name > snapshot 1

 Test Files  2 passed (2)
      Tests  6 passed (6)
   Start at  17:38:04
   Duration  1.71s (transform 69ms, setup 0ms, collect 67ms, tests 5ms, environment 0ms, prepare 588ms)


⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Unhandled Error ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯
Error: Obsolete snapshots found: [
  {
    "filePath": "/home/projects/vitest-dev-vitest-ap23doa8/test/suite.test.ts",
    "keys": [
      "suite name > snapshot 1"
    ]
  }
]

To surface this error as a test error, we can probably check it here and make it test file/suite error:

vitest/packages/vitest/src/runtime/runners/test.ts

Lines 64 to 65 in 0c2924b

	const result = await this.snapshotClient.finish(suite.file.filepath)
	await rpc().snapshotSaved(result)