std-env 4.2.0: isMacOS

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 std-env.isMacOS in pkg:npm/std-env@4.2.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/std-env@4.2.0
Demonstrate these symbols/APIs:
  - std-env.isMacOS

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:sha256:90757bda32109f9ad8d17dbe9333964f94787ba53d697f4433df14f051a71b7a","contract":["isMacOS is exported as a boolean flag from std-env","isMacOS evaluates to false in standard Linux environment","isMacOS is consistent with platform not starting with darwin","isMacOS evaluates to true when platform is darwin or begins with darwin case-insensitively","isMacOS evaluates to false for non-darwin platforms such as linux or win32"],"goal":"verify std-env.isMacOS in pkg:npm/std-env@4.2.0","kind":"HOW","packages":["pkg:npm/std-env@4.2.0"],"schemaVersion":1,"symbols":["std-env.isMacOS"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","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/std-env@4.2.0"],"schemaVersion":1,"subject":"pkg:npm/std-env@4.2.0","symbols":["std-env.isMacOS"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-std-env",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-std-env",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "std-env": "4.2.0"
      }
    },
    "node_modules/std-env": {
      "version": "4.2.0",
      "resolved": "https://registry.npmjs.org/std-env/-/std-env-4.2.0.tgz",
      "integrity": "sha512-oCUKSupKTHX53EyjDtuZQ64pjLJ6yYCtpmEw0goYxtjG9KpbRe8KAsl2tBUGU9DyMcJ0RwJ8GqJAFzMXcXW1Rw==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-std-env",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "license": "MIT-0",
  "dependencies": {
    "std-env": "4.2.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify std-env.isMacOS in pkg:npm/std-env@4.2.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/std-env@4.2.0"
  ],
  "symbols": [
    "std-env.isMacOS"
  ]
}

import assert from 'node:assert/strict';
import { isMacOS, platform } from 'std-env';

// 1. isMacOS is exported as a boolean flag from std-env
assert.strictEqual(typeof isMacOS, 'boolean', 'isMacOS must be a boolean');

// 2. isMacOS evaluates to false in standard Linux environment
assert.strictEqual(isMacOS, false, 'isMacOS must be false on Linux');

// 3. isMacOS is consistent with platform not starting with darwin
assert.strictEqual(platform, process.platform, 'platform should match process.platform');
assert.strictEqual(/^darwin/i.test(platform), false, 'platform must not start with darwin on Linux');

const origPlatformDescriptor = Object.getOwnPropertyDescriptor(process, 'platform');
const stdEnvUrl = import.meta.resolve('std-env');

try {
  // 4. isMacOS evaluates to true when platform is darwin or begins with darwin case-insensitively
  Object.defineProperty(process, 'platform', { value: 'darwin', configurable: true, writable: true });
  const modDarwin = await import(`${stdEnvUrl}?test=darwin`);
  assert.strictEqual(modDarwin.isMacOS, true, 'isMacOS must be true when platform is darwin');

  Object.defineProperty(process, 'platform', { value: 'Darwin', configurable: true, writable: true });
  const modDarwinUpper = await import(`${stdEnvUrl}?test=darwin-upper`);
  assert.strictEqual(modDarwinUpper.isMacOS, true, 'isMacOS must be true when platform is Darwin');

  // 5. isMacOS evaluates to false for non-darwin platforms such as linux or win32
  Object.defineProperty(process, 'platform', { value: 'linux', configurable: true, writable: true });
  const modLinux = await import(`${stdEnvUrl}?test=linux`);
  assert.strictEqual(modLinux.isMacOS, false, 'isMacOS must be false when platform is linux');

  Object.defineProperty(process, 'platform', { value: 'win32', configurable: true, writable: true });
  const modWin32 = await import(`${stdEnvUrl}?test=win32`);
  assert.strictEqual(modWin32.isMacOS, false, 'isMacOS must be false when platform is win32');
} finally {
  if (origPlatformDescriptor) {
    Object.defineProperty(process, 'platform', origPlatformDescriptor);
  }
}

console.log('All contract assertions passed.');