vuejs/core · error · Error

test case threw unexpected warnings:\n - ${nonAssertedWarnin

Error message

test case threw unexpected warnings:\n - ${nonAssertedWarnings.join('\n - ')}

What it means

Thrown by the vitest setup (scripts/setup-vitest.ts) in an afterEach hook. Vue's test suite mocks the dev-time `warn` function and tracks which warnings each test asserted with `expect(...).to.have.been.warned`. Any warning emitted but not asserted is treated as a test failure. setup-vitest.ts:101 lists the unasserted warnings in the error message.

Source

Thrown at scripts/setup-vitest.ts:101

beforeEach(() => {
  asserted.clear()
  warn = vi.spyOn(console, 'warn')
  warn.mockImplementation(() => {})
})

afterEach(() => {
  const assertedArray = Array.from(asserted)
  const nonAssertedWarnings = warn.mock.calls
    .map(args => args[0])
    .filter(received => {
      return !assertedArray.some(assertedMsg => {
        return received.includes(assertedMsg)
      })
    })
  warn.mockRestore()
  if (nonAssertedWarnings.length) {
    throw new Error(
      `test case threw unexpected warnings:\n - ${nonAssertedWarnings.join(
        '\n - ',
      )}`,
    )
  }
})

View on GitHub (pinned to a2b40db9a8)

Solutions

Assert the warning in the test using Vue's test-utils `expect(...).toHaveBeenWarned` / `expectWarning` helper so the warning is consumed.
Fix the underlying code so it no longer emits the unexpected warning.
If the warning is intentional but irrelevant to the test, suppress/assert it explicitly rather than ignoring it.
Re-run just the failing test with the vitest reporter to see the exact unasserted warning text, then address it.

Example fix

// before — test triggers a warning but doesn't assert
expect(root.html()).toContain('hi')

// after
expect(root.html()).toContain('hi')
expect(`Invalid prop`).toHaveBeenWarned()

Defensive patterns

Strategy: validation

Validate before calling

// In Vue's own test suite: assert every warning your test triggers.
// Use the test-utils helper to register expected warnings before they fire.
expect(`Invalid prop type`).toHaveBeenWarned()
// or assert the call count
expect(`Invalid prop type`).toHaveBeenWarnedLast()
// Clear between tests if needed
afterEach(() => clearWarn())

Type guard

function warningWasAsserted(received: string, asserted: string[]): boolean {
  return asserted.some(a => received.includes(a))
}

Prevention

Whenever a test triggers a dev warning, assert it with the test-utils warn helper.
After refactors that add warnings, update the test's asserted-warning list.
Fix the underlying code rather than letting stray warnings slip through.

When it happens

Trigger: A test triggers a Vue dev warning (e.g. a prop validation failure, a deprecation, a runtime warning) but does not assert it. Adding code that newly emits a warning to an existing test without updating its assertions.

Common situations: Refactoring that introduces a new warning in a code path exercised by tests; updating Vue and gaining a new dev warning; a test that previously relied on behavior now deprecated.

Related errors

AI-assisted analysis of vuejs/core@a2b40db9a8 (2026-08-12). Data as JSON: /api/errors/842ae40b7b5388d2. Report an issue: GitHub.