jest-util 30.4.1: interopRequireDefault

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 jest-util.interopRequireDefault in pkg:npm/jest-util@30.4.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/jest-util@30.4.1
Demonstrate these symbols/APIs:
  - jest-util.interopRequireDefault

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.

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{
  "name": "sample-jest-util-interop-require-default",
  "version": "1.0.0",
  "description": "Clean-room verification sample for jest-util interopRequireDefault",
  "type": "module",
  "private": true,
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "jest-util": "30.4.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify jest-util.interopRequireDefault in pkg:npm/jest-util@30.4.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/jest-util@30.4.1"
  ],
  "symbols": [
    "jest-util.interopRequireDefault"
  ]
}

import assert from 'node:assert/strict';
import { interopRequireDefault } from 'jest-util';

// 1. interopRequireDefault returns the object directly when obj.__esModule is true
{
  const esmModule = { __esModule: true, default: 'mainExport', helper: () => 'help' };
  const resolved = interopRequireDefault(esmModule);
  assert.strictEqual(resolved, esmModule);
  assert.strictEqual(resolved.default, 'mainExport');
  assert.strictEqual(resolved.helper(), 'help');
}

// 2. interopRequireDefault wraps non-esModule plain objects under the default property
{
  const cjsModule = { helper: () => 'help', value: 42 };
  const resolved = interopRequireDefault(cjsModule);
  assert.notStrictEqual(resolved, cjsModule);
  assert.strictEqual(resolved.default, cjsModule);
  assert.strictEqual(resolved.default.value, 42);
}

// 3. interopRequireDefault wraps functions without __esModule under the default property
{
  const fn = function targetFn(x) { return x * 2; };
  const resolved = interopRequireDefault(fn);
  assert.strictEqual(resolved.default, fn);
  assert.strictEqual(resolved.default(3), 6);
}

// 4. interopRequireDefault returns functions directly when fn.__esModule is true
{
  const esmFn = function esmExport() { return 'esm'; };
  esmFn.__esModule = true;
  esmFn.default = esmFn;
  const resolved = interopRequireDefault(esmFn);
  assert.strictEqual(resolved, esmFn);
}

// 5. interopRequireDefault wraps primitive values including numbers, strings, and booleans under the default property
{
  assert.deepStrictEqual(interopRequireDefault('hello'), { default: 'hello' });
  assert.deepStrictEqual(interopRequireDefault(123), { default: 123 });
  assert.deepStrictEqual(interopRequireDefault(true), { default: true });
}

// 6. interopRequireDefault wraps falsy values including null, undefined, 0, empty string, and false under the default property
{
  assert.deepStrictEqual(interopRequireDefault(null), { default: null });
  assert.deepStrictEqual(interopRequireDefault(undefined), { default: undefined });
  assert.deepStrictEqual(interopRequireDefault(0), { default: 0 });
  assert.deepStrictEqual(interopRequireDefault(''), { default: '' });
  assert.deepStrictEqual(interopRequireDefault(false), { default: false });
}

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