vitest-dev/vitest · error · Error

Expected is not a Number

Error message

Expected is not a Number

What it means

The CloseTo asymmetric matcher (expect.closeTo) requires its sample to be a Number; isA('Number', sample) rejects NaN and non-numbers. It is used for approximate floating-point equality within a precision.

Solutions

1. Pass a real number: expect.closeTo(1.5, 2).
2. Coerce validated numeric strings with Number(...) and confirm !Number.isNaN.
3. For BigInt values, convert explicitly or use a different matcher.

Example fix

// before
expect(value).toEqual(expect.closeTo('1.50', 2))
// after
expect(value).toEqual(expect.closeTo(1.5, 2))

function asCloseTo(sample, precision = 2) {
  if (typeof sample !== 'number' || Number.isNaN(sample)) {
    throw new TypeError('expect.closeTo needs a Number sample')
  }
  return expect.closeTo(sample, precision)
}

function isFiniteNumber(v): v is number {
  return typeof v === 'number' && !Number.isNaN(v)
}

When it happens

Trigger: expect.closeTo(sample) where sample is a string, null, object, or NaN.

Common situations: Passing a numeric string ('1.5') instead of a number; passing null from an optional field; passing a BigInt (not a Number).

Related errors

• any() expects to be passed a constructor function. Please…
• Expected is not a string
• Expected is not a String or a RegExp
• Precision is not a Number
• You must provide an array to

AI-assisted analysis of vitest-dev/vitest@1fa9837ec2 (2026-08-11). Data as JSON: /api/errors/f944ce2f2e759671. Report an issue: GitHub.

Appendix: source

Thrown at packages/expect/src/jest-asymmetric-matchers.ts:346

    return this.inverse ? !result : result
  }

  toString() {
    return `String${this.inverse ? 'Not' : ''}Matching`
  }

  getExpectedType() {
    return 'string'
  }
}

class CloseTo extends AsymmetricMatcher<number> {
  private readonly precision: number

  constructor(sample: number, precision = 2, inverse = false) {
    if (!isA('Number', sample)) {
      throw new Error('Expected is not a Number')
    }

    if (!isA('Number', precision)) {
      throw new Error('Precision is not a Number')
    }

    super(sample)
    this.inverse = inverse
    this.precision = precision
  }

  asymmetricMatch(other: number) {
    if (!isA('Number', other)) {
      return false
    }

    let result = false
    if (

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