jest-util 30.4.1: formatTime

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.formatTime 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.formatTime

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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import { formatTime } from 'jest-util';

export { formatTime };

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{
  "name": "sample-jest-util-format-time",
  "version": "1.0.0",
  "description": "Clean-room verification sample for jest-util formatTime",
  "type": "module",
  "private": true,
  "license": "MIT-0",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "jest-util": "30.4.1"
  }
}

{
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  "goal": "verify jest-util.formatTime in pkg:npm/jest-util@30.4.1",
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  "symbols": [
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}

import assert from 'node:assert/strict';
import { formatTime } from '../index.mjs';

// 1. formatTime formats duration in milliseconds with 'ms' unit by default
{
  assert.strictEqual(formatTime(0), '0 ms');
  assert.strictEqual(formatTime(42), '42 ms');
  assert.strictEqual(formatTime(1500), '1500 ms');
}

// 2. formatTime supports power prefix 0 to format duration in seconds
{
  assert.strictEqual(formatTime(0, 0), '0 s');
  assert.strictEqual(formatTime(10, 0), '10 s');
  assert.strictEqual(formatTime(1.5, 0), '1.5 s');
}

// 3. formatTime supports negative power prefixes for microseconds (-6) and nanoseconds (-9)
{
  assert.strictEqual(formatTime(50, -6), '50 μs');
  assert.strictEqual(formatTime(100, -9), '100 ns');
}

// 4. formatTime pads the formatted time string with leading spaces according to padLeftLength
{
  assert.strictEqual(formatTime(5, -3, 4), '   5 ms');
  assert.strictEqual(formatTime(123, -3, 4), ' 123 ms');
  assert.strictEqual(formatTime(1234, -3, 4), '1234 ms');
}

// 5. formatTime clamps out-of-range prefixPower values to supported minimum and maximum unit prefixes
{
  // prefixPower > 0 clamps to seconds ('s')
  assert.strictEqual(formatTime(5, 3), '5 s');
  assert.strictEqual(formatTime(5, 6), '5 s');

  // prefixPower < -9 clamps to nanoseconds ('ns')
  assert.strictEqual(formatTime(5, -12), '5 ns');
  assert.strictEqual(formatTime(5, -15), '5 ns');
}

console.log('All jest-util formatTime contract assertions passed successfully.');