@vitest/expect 2.1.9: isAsymmetric

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify @vitest/expect.isAsymmetric in pkg:npm/%40vitest/expect@2.1.9
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40vitest/expect@2.1.9
Demonstrate these symbols/APIs:
  - @vitest/expect.isAsymmetric

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:86307de15fdcdb264a87bbe0e5d3e3d060e4f90285bae8d1aa603f6bd9d1fe0c","contract":["isAsymmetric returns true for built-in Vitest asymmetric matchers including Any, Anything, ArrayContaining, ObjectContaining, StringContaining, and StringMatching","isAsymmetric returns true for custom objects and classes implementing an asymmetricMatch function","isAsymmetric returns false when asymmetricMatch property is not a function","isAsymmetric returns false for standard JavaScript objects, arrays, and primitive values","isAsymmetric returns false for functions, null, and undefined"],"goal":"verify @vitest/expect.isAsymmetric in pkg:npm/%40vitest/expect@2.1.9","kind":"HOW","packages":["pkg:npm/%40vitest/expect@2.1.9"],"schemaVersion":1,"symbols":["@vitest/expect.isAsymmetric"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40vitest/expect@2.1.9"],"schemaVersion":1,"subject":"pkg:npm/%40vitest/expect@2.1.9","symbols":["@vitest/expect.isAsymmetric"],"verifierAdapter":"node-typescript@1"}

import {
  isAsymmetric,
  Any,
  Anything,
  ArrayContaining,
  ObjectContaining,
  StringContaining,
  StringMatching,
  AsymmetricMatcher,
} from '@vitest/expect';

/**
 * Checks whether a value is an asymmetric matcher.
 * An asymmetric matcher is an object with an asymmetricMatch method.
 *
 * @param {unknown} value
 * @returns {boolean}
 */
export function checkIsAsymmetric(value) {
  return isAsymmetric(value);
}

/**
 * Creates a custom asymmetric matcher object.
 *
 * @param {(actual: unknown) => boolean} matchFn
 * @returns {{ asymmetricMatch: (actual: unknown) => boolean }}
 */
export function createCustomMatcher(matchFn) {
  return {
    asymmetricMatch: matchFn,
  };
}

export {
  isAsymmetric,
  Any,
  Anything,
  ArrayContaining,
  ObjectContaining,
  StringContaining,
  StringMatching,
  AsymmetricMatcher,
};

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{
  "name": "sample-vitest-expect-isasymmetric",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "description": "verify @vitest/expect.isAsymmetric in pkg:npm/%40vitest/expect@2.1.9",
  "main": "index.mjs",
  "license": "MIT-0",
  "dependencies": {
    "@vitest/expect": "2.1.9"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify @vitest/expect.isAsymmetric in pkg:npm/%40vitest/expect@2.1.9",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40vitest/expect@2.1.9"
  ],
  "symbols": [
    "@vitest/expect.isAsymmetric"
  ]
}

import assert from 'node:assert/strict';
import {
  isAsymmetric,
  Any,
  Anything,
  ArrayContaining,
  ObjectContaining,
  StringContaining,
  StringMatching,
  AsymmetricMatcher,
} from '@vitest/expect';
import {
  checkIsAsymmetric,
  createCustomMatcher,
} from '../index.mjs';

// 1. Built-in Vitest asymmetric matchers
{
  const anyMatcher = new Any(String);
  assert.equal(isAsymmetric(anyMatcher), true);
  assert.equal(checkIsAsymmetric(anyMatcher), true);

  const anythingMatcher = new Anything();
  assert.equal(isAsymmetric(anythingMatcher), true);
  assert.equal(checkIsAsymmetric(anythingMatcher), true);

  const arrayContainingMatcher = new ArrayContaining([1, 2]);
  assert.equal(isAsymmetric(arrayContainingMatcher), true);
  assert.equal(checkIsAsymmetric(arrayContainingMatcher), true);

  const objectContainingMatcher = new ObjectContaining({ key: 'val' });
  assert.equal(isAsymmetric(objectContainingMatcher), true);
  assert.equal(checkIsAsymmetric(objectContainingMatcher), true);

  const stringContainingMatcher = new StringContaining('sub');
  assert.equal(isAsymmetric(stringContainingMatcher), true);
  assert.equal(checkIsAsymmetric(stringContainingMatcher), true);

  const stringMatchingMatcher = new StringMatching(/^test/);
  assert.equal(isAsymmetric(stringMatchingMatcher), true);
  assert.equal(checkIsAsymmetric(stringMatchingMatcher), true);
}

// 2. Custom asymmetric matcher objects and classes
{
  const customMatcher = createCustomMatcher((actual) => typeof actual === 'number' && actual > 10);
  assert.equal(isAsymmetric(customMatcher), true);
  assert.equal(checkIsAsymmetric(customMatcher), true);
  assert.equal(customMatcher.asymmetricMatch(15), true);
  assert.equal(customMatcher.asymmetricMatch(5), false);

  class CustomClassMatcher extends AsymmetricMatcher {
    asymmetricMatch(actual) {
      return actual === 'expected-value';
    }
  }
  const classMatcher = new CustomClassMatcher('expected-value');
  assert.equal(isAsymmetric(classMatcher), true);
  assert.equal(checkIsAsymmetric(classMatcher), true);
  assert.equal(classMatcher.asymmetricMatch('expected-value'), true);
  assert.equal(classMatcher.asymmetricMatch('other'), false);
}

// 3. Objects where asymmetricMatch is not a function
{
  assert.equal(isAsymmetric({ asymmetricMatch: true }), false);
  assert.equal(checkIsAsymmetric({ asymmetricMatch: true }), false);

  assert.equal(isAsymmetric({ asymmetricMatch: 'not-a-function' }), false);
  assert.equal(checkIsAsymmetric({ asymmetricMatch: 'not-a-function' }), false);

  assert.equal(isAsymmetric({ asymmetricMatch: 12345 }), false);
  assert.equal(checkIsAsymmetric({ asymmetricMatch: 12345 }), false);

  assert.equal(isAsymmetric({ asymmetricMatch: null }), false);
  assert.equal(checkIsAsymmetric({ asymmetricMatch: null }), false);
}

// 4. Standard objects, arrays, and primitive values
{
  assert.equal(isAsymmetric({}), false);
  assert.equal(checkIsAsymmetric({}), false);

  assert.equal(isAsymmetric({ a: 1, b: 2 }), false);
  assert.equal(checkIsAsymmetric({ a: 1, b: 2 }), false);

  assert.equal(isAsymmetric([]), false);
  assert.equal(checkIsAsymmetric([]), false);

  assert.equal(isAsymmetric([1, 2, 3]), false);
  assert.equal(checkIsAsymmetric([1, 2, 3]), false);

  assert.equal(isAsymmetric('sample string'), false);
  assert.equal(checkIsAsymmetric('sample string'), false);

  assert.equal(isAsymmetric(42), false);
  assert.equal(checkIsAsymmetric(42), false);

  assert.equal(isAsymmetric(true), false);
  assert.equal(checkIsAsymmetric(true), false);

  assert.equal(isAsymmetric(Symbol('sym')), false);
  assert.equal(checkIsAsymmetric(Symbol('sym')), false);

  assert.equal(isAsymmetric(9007199254740991n), false);
  assert.equal(checkIsAsymmetric(9007199254740991n), false);
}

// 5. Functions, null, and undefined
{
  assert.equal(isAsymmetric(() => {}), false);
  assert.equal(checkIsAsymmetric(() => {}), false);

  assert.equal(isAsymmetric(function named() {}), false);
  assert.equal(checkIsAsymmetric(function named() {}), false);

  assert.equal(isAsymmetric(null), false);
  assert.equal(checkIsAsymmetric(null), false);

  assert.equal(isAsymmetric(undefined), false);
  assert.equal(checkIsAsymmetric(undefined), false);
}

console.log('Contract passed');