jest-util 30.4.1: isNonNullable

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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.isNonNullable 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.isNonNullable

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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'use strict';

const jestUtil = require('jest-util');
const isNonNullable = jestUtil.isNonNullable;

/**
 * Checks if a value is neither null nor undefined.
 * @template T
 * @param {T} value
 * @returns {boolean}
 */
function checkNonNullable(value) {
  return isNonNullable(value);
}

/**
 * Filters an array removing all null and undefined elements.
 * @template T
 * @param {Array<T>} array
 * @returns {Array<NonNullable<T>>}
 */
function filterNonNullable(array) {
  return array.filter(isNonNullable);
}

module.exports = {
  isNonNullable,
  checkNonNullable,
  filterNonNullable,
};

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{
  "name": "sample-jest-util-is-non-nullable",
  "version": "1.0.0",
  "description": "Minimal clean-room sample verifying isNonNullable in jest-util",
  "main": "index.js",
  "license": "MIT-0",
  "dependencies": {
    "jest-util": "30.4.1"
  }
}

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

import assert from 'node:assert/strict';
import { isNonNullable } from 'jest-util';
import { checkNonNullable, filterNonNullable } from '../index.js';

// 1. isNonNullable returns false for null and undefined
assert.equal(isNonNullable(null), false, 'isNonNullable(null) must be false');
assert.equal(checkNonNullable(null), false, 'checkNonNullable(null) must be false');
assert.equal(isNonNullable(undefined), false, 'isNonNullable(undefined) must be false');
assert.equal(checkNonNullable(undefined), false, 'checkNonNullable(undefined) must be false');

// 2. isNonNullable returns true for boolean values including false and true
assert.equal(isNonNullable(false), true, 'isNonNullable(false) must be true');
assert.equal(isNonNullable(true), true, 'isNonNullable(true) must be true');
assert.equal(checkNonNullable(false), true, 'checkNonNullable(false) must be true');
assert.equal(checkNonNullable(true), true, 'checkNonNullable(true) must be true');

// 3. isNonNullable returns true for numeric values including zero and NaN
assert.equal(isNonNullable(0), true, 'isNonNullable(0) must be true');
assert.equal(isNonNullable(-0), true, 'isNonNullable(-0) must be true');
assert.equal(isNonNullable(42), true, 'isNonNullable(42) must be true');
assert.equal(isNonNullable(NaN), true, 'isNonNullable(NaN) must be true');
assert.equal(isNonNullable(Infinity), true, 'isNonNullable(Infinity) must be true');

// 4. isNonNullable returns true for string values including empty strings
assert.equal(isNonNullable(''), true, 'isNonNullable("") must be true');
assert.equal(isNonNullable('hello'), true, 'isNonNullable("hello") must be true');
assert.equal(checkNonNullable(''), true, 'checkNonNullable("") must be true');

// 5. isNonNullable returns true for objects, arrays, and symbols
assert.equal(isNonNullable({}), true, 'isNonNullable({}) must be true');
assert.equal(isNonNullable([]), true, 'isNonNullable([]) must be true');
assert.equal(isNonNullable(Symbol('sample')), true, 'isNonNullable(Symbol) must be true');
assert.equal(isNonNullable(BigInt(0)), true, 'isNonNullable(0n) must be true');

// 6. isNonNullable acts as a predicate function in Array.prototype.filter to filter out null and undefined values
const raw = [0, null, 'a', undefined, false, '', null, NaN];
const filtered = raw.filter(isNonNullable);
assert.deepEqual(filtered, [0, 'a', false, '', NaN], 'filter must keep falsy non-nullable values and remove null/undefined');
const helperFiltered = filterNonNullable(raw);
assert.deepEqual(helperFiltered, [0, 'a', false, '', NaN], 'helper function filterNonNullable must match filter behavior');

console.log('Contract tests passed successfully.');