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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.
    1. 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.
ts
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:

diff
- import helpers from 'src/helpers'
+ import helpers from '../src/helpers'
    1. Make sure you don't have relative aliases. Vite treats them as relative to the file where the import is instead of the root.
ts
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
ts
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'.

ts
import { defineConfig } from 'vitest/config'

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

ts
import { defineConfig } from 'vitest/config'

export default defineConfig({
  test: {
    pool: 'forks',
  },
})
bash
vitest --pool=forks

Released under the MIT License.