jestjs/jest · error · Error

Precision is not a Number

Error message

Precision is not a Number

What it means

CloseTo's second constructor argument, precision (default 2), must be a Number; the constructor throws an Error if it is not. Precision controls the tolerance (10^-precision / 2) for the floating-point comparison, so a non-numeric precision would make the comparison meaningless.

Solutions

1. Omit precision to use the default (2), or pass a numeric value: `expect.closeTo(1.0, 3)`.
2. Coerce config-derived precision: `Number(precision)` and validate it is a finite integer.
3. Double-check argument order: closeTo(expectedNumber, precisionNumber).

Example fix

// before
expect(result).toEqual(expect.closeTo(1.0, '3')); // precision as string

// after
expect(result).toEqual(expect.closeTo(1.0, 3));

function withPrecision(value, precision) {
  if (precision !== undefined && (typeof precision !== 'number' || !Number.isFinite(precision))) {
    throw new TypeError('precision must be a number');
  }
  return precision === undefined ? expect.closeTo(value) : expect.closeTo(value, precision);
}

function isOptionalFiniteNumber(v: unknown): v is number | undefined {
  return v === undefined || (typeof v === 'number' && Number.isFinite(v));
}

When it happens

Trigger: Calling `expect.closeTo(value, precision)` where precision is a non-number (e.g. a string like '3', undefined passed positionally, or an object). Thrown at construction time.

Common situations: Passing precision as a string from config; forgetting the default and passing an undefined second arg explicitly; off-by-one argument ordering where precision lands in the wrong slot.

Related errors

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

AI-assisted analysis of jestjs/jest@8e6d128e4a (2026-08-10). Data as JSON: /api/errors/b8897cbd14639411. Report an issue: GitHub.

Appendix: source

Thrown at packages/expect/src/asymmetricMatchers.ts:355

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

  override 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: unknown) {
    if (!isA<number>('Number', other)) {
      return false;
    }
    let result: boolean;
    if (
      other === Number.POSITIVE_INFINITY &&
      this.sample === Number.POSITIVE_INFINITY
    ) {
      result = true; // Infinity - Infinity is NaN
    } else if (

View on GitHub (pinned to 8e6d128e4a)