[Bug]: Worker Existed Unexpectedly - No error messages and Flakey

[jrwpatterson]

Version

System:
    OS: macOS 26.3
    CPU: (8) arm64 Apple M1 Pro
    Memory: 528.98 MB / 32.00 GB
    Shell: 5.9 - /bin/zsh
  Browsers:
    Chrome: 145.0.7632.160
    Edge: 145.0.3800.97
    Safari: 26.3
  npmPackages:
    @rstest/core: ^0.9.1 => 0.9.1 
    @rstest/coverage-istanbul: ^0.3.0 => 0.3.0

Details

We are getting very flakey builds. They are super fast but some tests seem to be erroring out with Error: Worker exited unexpectedly

What makes matters worse is this happens on some computers and not others. We didn't get this with the same tests on Vitest.

We are running 3x faster so I don't want to drop out but :(

We can't reproduce it and there is no errors in the output

Reproduce link

its flakey

Reproduce Steps

can't its flakey

[9aoy]

Could you provide more information, such as your Node.js version and the rstest config? We recently found that rstest is not very stable on Node.js v20 when running in no-isolate mode.

[jrwpatterson]

Sure node 22 and rstest 0.91
Seems to happen on faster machines not slower machines

Here is the UI version

import { dirname, resolve } from 'node:path';
import { fileURLToPath } from 'node:url';
import { defineConfig } from '@rstest/core';

const __dirname = dirname(fileURLToPath(import.meta.url));
const env =
  (
    Reflect.get(globalThis, 'process') as
      | { env?: Record<string, string | undefined> }
      | undefined
  )?.env ?? {};
const isCI = env.REPO_NAME != null || env.CI === 'true';

const config = defineConfig({
  name: 'ui',
  globals: true,
  testEnvironment: 'happy-dom',
  source: {
    tsconfigPath: './tsconfig.spec.json',
  },
  resolve: {
    dedupe: ['react', 'react-dom', 'react-router', 'react-router-dom'],
    alias: {
      'custidentificationsecurityquestions-v1/OneIdWidget': resolve(
        __dirname,
        './test-support/mocks/OneIdWidget.tsx',
      ),
      '@mep-ui/framework-router-addon': resolve(
        __dirname,
        './test-support/mocks/framework-router-addon.ts',
      ),
    },
  },
  setupFiles: [
    '../test-support/rstest-globals.ts',
    './test-support/setupTests.js',
    'vitest-localstorage-mock',
  ],
  coverage: {
    enabled: isCI,
    include: ['src/**/*.{js,jsx,ts,tsx}'],
    thresholds: {
      global: {
        lines: 80,
        branches: 80,
        functions: 80,
        statements: 80,
      },
    },
    exclude: [
      '**/serviceWorker.js',
      '**/tools/**',
      '**/test-support/**',
      '**/__snapshots__/**',
      '**/__fixtures__/**',
      '**/node_modules/**',
      'src/api/generated/**',
      '**/index.{js,jsx,ts,tsx}',
      'src/types/**',
    ],
    reporters: ['json', 'lcov', 'text', 'html'],

    reportsDirectory: '../coverage/ui',
  },
  tools: {
    swc: {
      jsc: {
        transform: {
          react: {
            runtime: 'automatic',
          },
        },
      },
    },
  },
  reporters: isCI
    ? ['default', ['junit', { outputPath: 'coverage/ui/junit.xml' }]]
    : ['default'],
});

// biome-ignore lint/style/noDefaultExport: <test>
export default config;

here is the api

import { resolve } from 'node:path';
import { defineConfig } from '@rstest/core';

const env =
  (
    Reflect.get(globalThis, 'process') as
      | { env?: Record<string, string | undefined> }
      | undefined
  )?.env ?? {};
const isCI = env.REPO_NAME != null || env.CI === 'true';

const config = defineConfig({
  name: 'api',
  globals: true,
  testEnvironment: 'node',
  source: {
    tsconfigPath: './tsconfig.spec.json',
  },
  resolve: {
    dedupe: ['@trpc/server'],
    alias: {
      '@mep-node/framework-constants': resolve(
        __dirname,
        '../test-support/framework-constants-mock.js',
      ),
    },
  },
  setupFiles: ['../test-support/rstest-globals.ts'],
  coverage: {
    enabled: isCI,
    include: ['server/**/*.{js,ts,cjs,mjs}'],
    thresholds: {
      global: {
        lines: 80,
        branches: 80,
        functions: 80,
        statements: 80,
      },
    },
    reporters: ['json', 'lcov', 'text', 'html'],
    exclude: [
      'server/**/*/index.ts',
      'server/**/*/evaluatePoliciesController.ts',
      'server/**/*/constants.ts',
      'server/generated/**/*.{js,ts,cjs,mjs}',
      'server/api/**/__fixtures__/**/*.{js,ts,cjs,mjs}',
      'server/api/types/**',
      'server/api/schema/*.{js,ts,cjs,mjs}',
      'server/api/middleware/mockDataMiddleware.ts',
    ],
    reportsDirectory: '../coverage/api',
  },

  reporters: isCI
    ? ['default', ['junit', { outputPath: 'coverage/api/junit.xml' }]]
    : ['default'],
  exclude: ['node_modules', 'server/api/controllers/__tests__/example'],
});

export default config;

And here is the route config

import { defineConfig } from '@rstest/core';

const config = defineConfig({
  projects: ['./api', './ui'],
});

// biome-ignore lint/style/noDefaultExport: <test>
export default config;