check-error 2.1.3: getMessage

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 check-error.getMessage in pkg:npm/check-error@2.1.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/check-error@2.1.3
Demonstrate these symbols/APIs:
  - check-error.getMessage

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:f90b9ddde306004fc0a10c7b9f9bb32e33b5bd3c89c1d987ec0a20685269bc5e","contract":["getMessage returns the message string from an Error instance","getMessage returns the string itself when passed a plain string error","getMessage returns the message property from custom error-like objects","getMessage returns an empty string when the error instance has no message property or message is empty","getMessage returns an empty string when the error-like object has no message property","getMessage returns an empty string when errorLike is null or undefined","getMessage returns an empty string for primitive non-string values without message"],"goal":"verify check-error.getMessage in pkg:npm/check-error@2.1.3","kind":"HOW","packages":["pkg:npm/check-error@2.1.3"],"schemaVersion":1,"symbols":["check-error.getMessage"]},"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/check-error@2.1.3"],"schemaVersion":1,"subject":"pkg:npm/check-error@2.1.3","symbols":["check-error.getMessage"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-check-error",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-check-error",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "check-error": "2.1.3"
      }
    },
    "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",
      "engines": {
        "node": ">= 16"
      }
    }
  }
}

{
  "name": "sample-check-error",
  "version": "1.0.0",
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "check-error": "2.1.3"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify check-error.getMessage in pkg:npm/check-error@2.1.3",
  "kind": "HOW",
  "packages": [
    "pkg:npm/check-error@2.1.3"
  ],
  "symbols": [
    "check-error.getMessage"
  ]
}

import assert from 'node:assert/strict';
import { getMessage } from 'check-error';

// 1. getMessage returns the message string from an Error instance
const err = new Error('Database connection failed');
assert.equal(getMessage(err), 'Database connection failed');
assert.equal(getMessage(new TypeError('Invalid argument type')), 'Invalid argument type');
assert.equal(getMessage(new RangeError('Index out of bounds')), 'Index out of bounds');

// 2. getMessage returns the string itself when passed a plain string error
assert.equal(getMessage('simple error message'), 'simple error message');
assert.equal(getMessage(''), '');

// 3. getMessage returns the message property from custom error-like objects
assert.equal(getMessage({ message: 'custom error object' }), 'custom error object');
assert.equal(getMessage({ message: 'another error', code: 500 }), 'another error');

// 4. getMessage returns an empty string when the error instance has no message property or message is empty
assert.equal(getMessage(new Error()), '');
assert.equal(getMessage(new Error('')), '');

// 5. getMessage returns an empty string when the error-like object has no message property
assert.equal(getMessage({}), '');
assert.equal(getMessage({ name: 'CustomError', code: 404 }), '');

// 6. getMessage returns an empty string when errorLike is null or undefined
assert.equal(getMessage(null), '');
assert.equal(getMessage(undefined), '');

// 7. getMessage returns an empty string for primitive non-string values without message
assert.equal(getMessage(404), '');
assert.equal(getMessage(true), '');
assert.equal(getMessage(Symbol('err')), '');

console.log('All check-error.getMessage contract assertions passed.');