assertion-error 2.0.1: AssertionError

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 assertion-error.AssertionError in 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:
  - assertion-error.AssertionError

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:sha256:1e1151c1420bd4f027a9327bedce2f5e12ee7dbccd4fee71f3220fdd3f13055f","contract":["AssertionError inherits from Error with name 'AssertionError' and ok false","AssertionError defaults message to 'Unspecified AssertionError' when omitted","AssertionError copies custom properties from props without overwriting prototype properties","AssertionError accepts ssf function to elide stack frames above call site","AssertionError.toJSON serializes error properties and includes or omits stack based on argument"],"goal":"verify assertion-error.AssertionError in pkg:npm/assertion-error@2.0.1","kind":"HOW","packages":["pkg:npm/assertion-error@2.0.1"],"schemaVersion":1,"symbols":["assertion-error.AssertionError"]},"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":["assertion-error.AssertionError"],"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 assertion-error.AssertionError in pkg:npm/assertion-error@2.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/assertion-error@2.0.1"
  ],
  "symbols": [
    "assertion-error.AssertionError"
  ]
}

import assert from 'node:assert';
import { AssertionError } from 'assertion-error';

// 1. AssertionError inherits from Error with name 'AssertionError' and ok false
const err = new AssertionError('custom failure');
assert.strictEqual(err instanceof Error, true);
assert.strictEqual(err.name, 'AssertionError');
assert.strictEqual(err.ok, false);
assert.strictEqual(err.message, 'custom failure');

// 2. AssertionError defaults message to 'Unspecified AssertionError' when omitted
const defaultErr = new AssertionError();
assert.strictEqual(defaultErr.message, 'Unspecified AssertionError');
assert.strictEqual(defaultErr.ok, false);

// 3. AssertionError copies custom properties from props without overwriting prototype properties
const propsErr = new AssertionError('diff failure', {
  actual: 42,
  expected: 99,
  showDiff: true,
  name: 'ignoredCustomName'
});
assert.strictEqual(propsErr.actual, 42);
assert.strictEqual(propsErr.expected, 99);
assert.strictEqual(propsErr.showDiff, true);
assert.strictEqual(propsErr.name, 'AssertionError');

// 4. AssertionError accepts ssf function to elide stack frames above call site
function helperFunction() {
  return new AssertionError('failed inside helper', {}, helperFunction);
}
const elidedErr = helperFunction();
assert.strictEqual(typeof elidedErr.stack, 'string');
assert.ok(!elidedErr.stack.includes('helperFunction'));

// 5. AssertionError.toJSON serializes error properties and includes or omits stack based on argument
const jsonWithStack = propsErr.toJSON();
assert.strictEqual(jsonWithStack.name, 'AssertionError');
assert.strictEqual(jsonWithStack.message, 'diff failure');
assert.strictEqual(jsonWithStack.ok, false);
assert.strictEqual(jsonWithStack.actual, 42);
assert.strictEqual(jsonWithStack.expected, 99);
assert.strictEqual(jsonWithStack.showDiff, true);
assert.strictEqual(typeof jsonWithStack.stack, 'string');

const jsonNoStack = propsErr.toJSON(false);
assert.strictEqual(jsonNoStack.stack, undefined);
assert.strictEqual(jsonNoStack.actual, 42);
assert.strictEqual(jsonNoStack.ok, false);

console.log('Contract passed');