assertion-error 2.0.1: AssertionError, AssertionResult

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 pkg:npm/assertion-error@2.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/assertion-error@2.0.1
Demonstrate these symbols/APIs:
  - AssertionError
  - AssertionResult

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:sha256:004abee1f6c7aad513ae08caca22120db801bf469cf6f42ef836a01a0a7db636","contract":["AssertionError extends Error with name 'AssertionError' and ok false","AssertionError attaches extra properties passed via constructor props argument","AssertionError.toJSON() serializes name, ok, message, extra props, and stack","AssertionResult has name 'AssertionResult' and ok true without extending Error"],"goal":"verify pkg:npm/assertion-error@2.0.1","kind":"HOW","packages":["pkg:npm/assertion-error@2.0.1"],"schemaVersion":1,"symbols":["AssertionError","AssertionResult"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/assertion-error@2.0.1"],"schemaVersion":1,"subject":"pkg:npm/assertion-error@2.0.1","symbols":["AssertionError","AssertionResult"],"verifierAdapter":"node-typescript@1"}

{
  "name": "assertion-error-sample",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "assertion-error-sample",
      "version": "1.0.0",
      "dependencies": {
        "assertion-error": "2.0.1"
      }
    },
    "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": {
        "node": ">=12"
      }
    }
  }
}

{
  "name": "assertion-error-sample",
  "version": "1.0.0",
  "type": "module",
  "dependencies": {
    "assertion-error": "2.0.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/assertion-error@2.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/assertion-error@2.0.1"
  ],
  "symbols": [
    "AssertionError",
    "AssertionResult"
  ]
}

import { AssertionError, AssertionResult } from 'assertion-error';

export function assertEqual(actual, expected, message) {
  if (actual === expected) {
    return new AssertionResult({ actual, expected, message });
  }
  throw new AssertionError(message || `expected ${expected} but got ${actual}`, {
    actual,
    expected,
    showDiff: true
  });
}

import assert from 'node:assert';
import { AssertionError, AssertionResult } from 'assertion-error';
import { assertEqual } from '../src/index.mjs';

// 1. AssertionError is an instance of Error with name 'AssertionError' and ok === false
const err = new AssertionError('custom error');
assert.strictEqual(err instanceof Error, true);
assert.strictEqual(err.name, 'AssertionError');
assert.strictEqual(err.ok, false);
assert.strictEqual(err.message, 'custom error');

// 2. Default message when omitted
const errDefault = new AssertionError();
assert.strictEqual(errDefault.message, 'Unspecified AssertionError');

// 3. Custom properties attached via props
const errProps = new AssertionError('failure', {
  actual: 10,
  expected: 20,
  showDiff: true
});
assert.strictEqual(errProps.actual, 10);
assert.strictEqual(errProps.expected, 20);
assert.strictEqual(errProps.showDiff, true);

// 4. toJSON() returns serialized assertion error with name, ok, and stack
const json = errProps.toJSON();
assert.strictEqual(json.name, 'AssertionError');
assert.strictEqual(json.ok, false);
assert.strictEqual(json.message, 'failure');
assert.strictEqual(json.actual, 10);
assert.strictEqual(typeof json.stack, 'string');

// 5. toJSON(false) excludes stack
const jsonNoStack = errProps.toJSON(false);
assert.strictEqual(jsonNoStack.stack, undefined);
assert.strictEqual(jsonNoStack.name, 'AssertionError');
assert.strictEqual(jsonNoStack.ok, false);

// 6. AssertionResult has name 'AssertionResult', ok === true, and does not extend Error
const res = new AssertionResult({ passed: true, actual: 5, expected: 5 });
assert.strictEqual(res instanceof Error, false);
assert.strictEqual(res.name, 'AssertionResult');
assert.strictEqual(res.ok, true);
assert.strictEqual(res.passed, true);
assert.strictEqual(res.actual, 5);

const resJson = res.toJSON();
assert.strictEqual(resJson.name, 'AssertionResult');
assert.strictEqual(resJson.ok, true);
assert.strictEqual(resJson.passed, true);

// 7. Helper assertEqual behavior
const success = assertEqual(42, 42, 'numbers match');
assert.strictEqual(success.ok, true);
assert.strictEqual(success.name, 'AssertionResult');

assert.throws(
  () => assertEqual(1, 2, 'mismatch'),
  (thrown) => {
    return (
      thrown instanceof AssertionError &&
      thrown.name === 'AssertionError' &&
      thrown.ok === false &&
      thrown.actual === 1 &&
      thrown.expected === 2 &&
      thrown.message === 'mismatch'
    );
  }
);