@vitest/expect 2.1.9: expect

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 expect 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:
  - expect

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:sha256:90e607ce4e1b84935e1dc9b36c7ce8db05969b9a5c94b09e7f0f04d8d3954633","contract":["expect performs strict primitive equality and .not inversion","toEqual and toStrictEqual perform deep object and array structural equality assertions","toMatchObject and toHaveProperty verify subset structures and nested object properties","toContain and toContainEqual assert element presence and membership in arrays and strings","toBeGreaterThan, toBeLessThan, and toBeCloseTo validate numeric relationships and floating point values","toBeTypeOf and toSatisfy evaluate type classifications and custom predicate functions","toThrow verifies exception throwing and error type matching","Asymmetric matchers stringContaining, stringMatching, objectContaining, arrayContaining, any, and anything match partial values","expect.extend registers custom matchers with custom pass and failure message logic","getState and setState inspect and update matcher execution context"],"goal":"verify expect in pkg:npm/%40vitest/expect@2.1.9","kind":"HOW","packages":["pkg:npm/%40vitest/expect@2.1.9"],"schemaVersion":1,"symbols":["expect"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","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":["expect"],"verifierAdapter":"node-typescript@1"}

import * as chai from 'chai';
import {
  JestChaiExpect,
  JestAsymmetricMatchers,
  JestExtend,
  getState,
  setState,
  equals,
  isA,
  isAsymmetric,
  hasAsymmetric,
  StringContaining,
  StringMatching,
  ObjectContaining,
  ArrayContaining,
  Any,
  Anything
} from '@vitest/expect';

chai.use(JestChaiExpect);
chai.use(JestAsymmetricMatchers);
chai.use(JestExtend);

export const expect = chai.expect;

export {
  JestChaiExpect,
  JestAsymmetricMatchers,
  JestExtend,
  getState,
  setState,
  equals,
  isA,
  isAsymmetric,
  hasAsymmetric,
  StringContaining,
  StringMatching,
  ObjectContaining,
  ArrayContaining,
  Any,
  Anything
};

{
  "name": "sample-vitest-expect",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-vitest-expect",
      "version": "1.0.0",
      "dependencies": {
        "@vitest/expect": "2.1.9"
      }
    },
    "node_modules/@vitest/expect": {
      "version": "2.1.9",
      "resolved": "https://registry.npmjs.org/@vitest/expect/-/expect-2.1.9.tgz",
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      "license": "MIT",
      "dependencies": {
        "@vitest/spy": "2.1.9",
        "@vitest/utils": "2.1.9",
        "chai": "^5.1.2",
        "tinyrainbow": "^1.2.0"
      },
      "funding": {
        "url": "https://opencollective.com/vitest"
      }
    },
    "node_modules/@vitest/pretty-format": {
      "version": "2.1.9",
      "resolved": "https://registry.npmjs.org/@vitest/pretty-format/-/pretty-format-2.1.9.tgz",
      "integrity": "sha512-KhRIdGV2U9HOUzxfiHmY8IFHTdqtOhIzCpd8WRdJiE7D/HUcZVD0EgQCVjm+Q9gkUXWgBvMmTtZgIG48wq7sOQ==",
      "license": "MIT",
      "dependencies": {
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      },
      "funding": {
        "url": "https://opencollective.com/vitest"
      }
    },
    "node_modules/@vitest/spy": {
      "version": "2.1.9",
      "resolved": "https://registry.npmjs.org/@vitest/spy/-/spy-2.1.9.tgz",
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      "license": "MIT",
      "dependencies": {
        "tinyspy": "^3.0.2"
      },
      "funding": {
        "url": "https://opencollective.com/vitest"
      }
    },
    "node_modules/@vitest/utils": {
      "version": "2.1.9",
      "resolved": "https://registry.npmjs.org/@vitest/utils/-/utils-2.1.9.tgz",
      "integrity": "sha512-v0psaMSkNJ3A2NMrUEHFRzJtDPFn+/VWZ5WxImB21T9fjucJRmS7xCS3ppEnARb9y11OAzaD+P2Ps+b+BGX5iQ==",
      "license": "MIT",
      "dependencies": {
        "@vitest/pretty-format": "2.1.9",
        "loupe": "^3.1.2",
        "tinyrainbow": "^1.2.0"
      },
      "funding": {
        "url": "https://opencollective.com/vitest"
      }
    },
    "node_modules/assertion-error": {
      "version": "2.0.1",
      "resolved": "https://registry.npmjs.org/assertion-error/-/assertion-error-2.0.1.tgz",
      "integrity": "sha512-Izi8RQcffqCeNVgFigKli1ssklIbpHnCYc6AknXGYoB6grJqyeby7jv12JUQgmTAnIDnbck1uxksT4dzN3PWBA==",
      "license": "MIT",
      "engines": {
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    },
    "node_modules/chai": {
      "version": "5.3.3",
      "resolved": "https://registry.npmjs.org/chai/-/chai-5.3.3.tgz",
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      "license": "MIT",
      "dependencies": {
        "assertion-error": "^2.0.1",
        "check-error": "^2.1.1",
        "deep-eql": "^5.0.1",
        "loupe": "^3.1.0",
        "pathval": "^2.0.0"
      },
      "engines": {
        "node": ">=18"
      }
    },
    "node_modules/check-error": {
      "version": "2.1.3",
      "resolved": "https://registry.npmjs.org/check-error/-/check-error-2.1.3.tgz",
      "integrity": "sha512-PAJdDJusoxnwm1VwW07VWwUN1sl7smmC3OKggvndJFadxxDRyFJBX/ggnu/KE4kQAB7a3Dp8f/YXC1FlUprWmA==",
      "license": "MIT",
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    },
    "node_modules/deep-eql": {
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      "integrity": "sha512-h5k/5U50IJJFpzfL6nO9jaaumfjO/f2NjK/oYB2Djzm4p9L+3T9qWpZqZ2hAbLPuuYq9wrU08WQyBTL5GbPk5Q==",
      "license": "MIT",
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      "license": "MIT"
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      "resolved": "https://registry.npmjs.org/pathval/-/pathval-2.0.1.tgz",
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      "license": "MIT",
      "engines": {
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    "node_modules/tinyrainbow": {
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      "license": "MIT",
      "engines": {
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      }
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  }
}

{
  "name": "sample-vitest-expect",
  "version": "1.0.0",
  "description": "Clean-room verification sample for expect in @vitest/expect",
  "type": "module",
  "main": "index.mjs",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "@vitest/expect": "2.1.9"
  }
}

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

import assert from 'node:assert/strict';
import {
  expect,
  getState,
  setState,
  equals,
  isA,
  isAsymmetric,
  hasAsymmetric,
  StringContaining,
  StringMatching,
  ObjectContaining,
  ArrayContaining,
  Any,
  Anything
} from '../index.mjs';

// 1. Basic expect assertion function and .not negation
{
  assert.equal(typeof expect, 'function');
  expect(42).toBe(42);
  expect('vitest').toBe('vitest');
  expect(true).toBe(true);
  expect(false).toBe(false);
  expect(null).toBeNull();
  expect(undefined).toBeUndefined();
  expect(NaN).toBeNaN();
  expect(10).not.toBe(20);
  expect('hello').not.toBe('world');
}

// 2. toEqual and toStrictEqual deep equality assertions
{
  const obj1 = { id: 1, tags: ['a', 'b'], meta: { count: 3 } };
  const obj2 = { id: 1, tags: ['a', 'b'], meta: { count: 3 } };
  expect(obj1).toEqual(obj2);
  expect(obj1).toStrictEqual(obj2);
  expect([1, 2, 3]).toEqual([1, 2, 3]);
  expect([1, 2]).not.toEqual([1, 3]);
}

// 3. toMatchObject and toHaveProperty structural inspection
{
  const user = { id: 100, name: 'Alex', profile: { role: 'admin', level: 5 } };
  expect(user).toMatchObject({ name: 'Alex', profile: { role: 'admin' } });
  expect(user).toHaveProperty('profile.role', 'admin');
  expect(user).toHaveProperty('id', 100);
}

// 4. toContain and toContainEqual containment assertions
{
  expect(['apple', 'banana', 'orange']).toContain('banana');
  expect('javascript string matcher').toContain('string');
  expect([{ key: 'a' }, { key: 'b' }]).toContainEqual({ key: 'b' });
  expect([10, 20, 30]).toHaveLength(3);
  expect('hello').toHaveLength(5);
}

// 5. Numerical range assertions (toBeGreaterThan, toBeLessThan, toBeCloseTo)
{
  expect(15).toBeGreaterThan(10);
  expect(15).toBeGreaterThanOrEqual(15);
  expect(5).toBeLessThan(10);
  expect(5).toBeLessThanOrEqual(5);
  expect(0.1 + 0.2).toBeCloseTo(0.3, 5);
}

// 6. Type and predicate assertions (toBeTypeOf, toSatisfy)
{
  expect('test-string').toBeTypeOf('string');
  expect(12345).toBeTypeOf('number');
  expect(true).toBeTypeOf('boolean');
  expect(Symbol('vitest')).toBeTypeOf('symbol');
  expect(20).toSatisfy(n => n % 5 === 0);
  expect('admin@example.com').toSatisfy(s => s.includes('@'));
}

// 7. Exception assertions (toThrow, toThrowError)
{
  expect(() => {
    throw new Error('invalid operation');
  }).toThrow('invalid operation');

  expect(() => {
    throw new TypeError('invalid argument');
  }).toThrow(TypeError);

  expect(() => {
    // no error thrown
  }).not.toThrow();
}

// 8. Asymmetric matchers attached to expect and constructor classes
{
  expect('sample-test-case').toEqual(expect.stringContaining('test'));
  expect('vitest-2.1.9').toEqual(expect.stringMatching(/^vitest-\d+\.\d+\.\d+$/));
  expect({ x: 1, y: 2, extra: true }).toEqual(expect.objectContaining({ x: 1, y: 2 }));
  expect([1, 2, 3, 4]).toEqual(expect.arrayContaining([2, 4]));
  expect('hello').toEqual(expect.any(String));
  expect(99).toEqual(expect.any(Number));
  expect({ custom: true }).toEqual(expect.anything());

  // Using exported matcher constructors
  expect('prefix-val-suffix').toEqual(new StringContaining('val'));
  expect('abc-123').toEqual(new StringMatching(/^abc-\d+$/));
  expect({ a: 10, b: 20 }).toEqual(new ObjectContaining({ a: 10 }));
  expect([10, 20, 30]).toEqual(new ArrayContaining([20]));
  expect('str').toEqual(new Any(String));
  expect({}).toEqual(new Anything());
}

// 9. expect.extend registers custom matchers
{
  expect.extend(expect, {
    toBeWithinRange(received, floor, ceiling) {
      const pass = received >= floor && received <= ceiling;
      return {
        pass,
        message: () => `expected ${received} ${pass ? 'not ' : ''}to be within range [${floor}, ${ceiling}]`,
      };
    },
  });

  expect(50).toBeWithinRange(1, 100);
  expect(150).not.toBeWithinRange(1, 100);
}

// 10. getState and setState lifecycle management
{
  setState({ currentTestName: 'expect-suite-verification', assertionCount: 10 }, expect);
  const state = getState(expect);
  assert.equal(state.currentTestName, 'expect-suite-verification');
  assert.equal(state.assertionCount, 10);

  assert.equal(equals({ k: 1 }, { k: 1 }), true);
  assert.equal(equals({ k: 1 }, { k: 2 }), false);
  assert.equal(isA('String', 'hello'), true);
  assert.equal(isA('Number', 42), true);
  assert.equal(isAsymmetric(new Any(String)), true);
  assert.equal(hasAsymmetric({ matcher: new Any(Number) }), true);
}

console.log('All @vitest/expect contract assertions passed successfully.');