vitest-dev/vitest · error · Error

' ' cannot be used without test context

Error message

'${getAssertionName(obj)}' cannot be used without test context

What it means

Thrown by `getTest` when a snapshot assertion (`toMatchSnapshot`, `toMatchInlineSnapshot`, `toMatchFileSnapshot`, `toThrowErrorMatchingSnapshot[InlineSnapshot]`) is called but the `vitest-test` flag is missing from the Chai assertion object. Vitest attaches the active `Test` instance to that flag at assertion-creation time; without it the snapshot cannot be attributed to a test file/name, so the call is rejected. The message names the offending assertion.

Solutions

Move the `expect(...).toMatchSnapshot()` call inside an `it`/`test` body so the test context is active.
If inside an async callback, ensure it is awaited within the test so the context is preserved.
Import `expect` from `vitest` (not a standalone copy) so the test-aware instance is used.

Example fix

// before (module scope)
expect(value).toMatchSnapshot()

// after
test('snapshots value', () => {
  expect(value).toMatchSnapshot()
})

Defensive patterns

Strategy: validation

Validate before calling

import { getWorkerState } from 'vitest'
function inTestContext() {
  return !!getWorkerState()?.currentTask
}
if (!inTestContext()) throw new Error('snapshot must run inside a test')
expect(value).toMatchSnapshot()

Prevention

Keep expect(...).toMatchSnapshot() inside an it/test body.
Import expect from vitest so the test-aware instance is used.
Avoid module-level or detached-worker snapshot calls.

When it happens

Trigger: Using `expect(...).toMatchSnapshot()` outside of a running test (e.g. at module top level, in a worker, inside a plain script, in a setup hook that runs outside test context); calling snapshot assertions via a manually constructed `expect` that bypasses Vitest's test-aware wrapper.

Common situations: Calling `expect` inside module-level code or `globalThis` callbacks; using `expect` from a different package than the test runner; extracting `expect` into a helper that runs outside the test's async context; running assertion code in a detached worker.

Related errors

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/e4f6733187030be1. Report an issue: GitHub.

Appendix: source

Thrown at packages/vitest/src/integrations/snapshot/chai.ts:68

  return {
    filepath: test.file.filepath,
    name: getNames(test).slice(1).join(' > '),
    testId: test.id,
  }
}

function getAssertionName(assertion: Chai.Assertion): string {
  const name = chai.util.flag(assertion, '_name') as string | undefined
  if (!name) {
    throw new Error('Assertion name is not set. This is a bug in Vitest. Please, open a new issue with reproduction.')
  }
  return name
}

function getTest(obj: Chai.Assertion) {
  const test = chai.util.flag(obj, 'vitest-test') as Test | undefined
  if (!test) {
    throw new Error(`'${getAssertionName(obj)}' cannot be used without test context`)
  }
  if (test.fails) {
    throw new TestSyntaxError(`'${getAssertionName(obj)}' cannot be used with 'test.fails'`)
  }
  return test
}

function validateAssertion(assertion: Chai.Assertion): void {
  if (chai.util.flag(assertion, 'negate')) {
    throw new Error(`${getAssertionName(assertion)} cannot be used with "not"`)
  }
}

export const SnapshotPlugin: ChaiPlugin = (chai, utils) => {
  for (const key of ['matchSnapshot', 'toMatchSnapshot']) {
    utils.addMethod(
      chai.Assertion.prototype,
      key,

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