Common Errors

Cannot find module './relative-path'

If you receive an error that module cannot be found, it might mean several different things:

• 1. You misspelled the path. Make sure the path is correct.
• 2. It's possible that you rely on baseUrl in your tsconfig.json. Vite doesn't take into account tsconfig.json by default, so you might need to install vite-tsconfig-paths yourself, if you rely on this behaviour.

import { defineConfig } from 'vitest/config'
import tsconfigPaths from 'vite-tsconfig-paths'

export default defineConfig({
  plugins: [tsconfigPaths()]
})

Or rewrite your path to not be relative to root:

- import helpers from 'src/helpers'
+ import helpers from '../src/helpers'

• 3. Make sure you don't have relative aliases. Vite treats them as relative to the file where the import is instead of the root.

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    alias: {
      '@/': './src/', 
      '@/': new URL('./src/', import.meta.url).pathname, 
    }
  }
})

Cannot mock "./mocked-file.js" because it is already loaded

This error happens when vi.mock method is called on a module that was already loaded. Vitest throws this error because this call has no effect since cached modules are preferred.

Remember that vi.mock is always hoisted - it means that the module was loaded before the test file started executing - most likely in a setup file. To fix the error, remove the import or clear the cache at the end of a setup file - beware that setup file and your test file will reference different modules in that case.

setupFile.js

import { vi } from 'vitest'
import { sideEffect } from './mocked-file.js'

sideEffect()

vi.resetModules()

Failed to terminate worker

This error can happen when NodeJS's fetch is used with default pool: 'threads'. This issue is tracked on issue Timeout abort can leave process(es) running in the background #3077.

As work-around you can switch to pool: 'forks' or pool: 'vmForks'.

vitest.config.js

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    pool: 'forks',
  },
})

CLI

vitest --pool=forks

Segfaults and native code errors

Running native NodeJS modules in pool: 'threads' can run into cryptic errors coming from the native code.

• Segmentation fault (core dumped)
• thread '<unnamed>' panicked at 'assertion failed
• Abort trap: 6
• internal error: entered unreachable code

In these cases the native module is likely not built to be multi-thread safe. As work-around, you can switch to pool: 'forks' which runs the test cases in multiple node:child_process instead of multiple node:worker_threads.

vitest.config.js

import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    pool: 'forks',
  },
})

CLI

vitest --pool=forks