CodeSampleX

Sample

@jest/fake-timers 29.7.0: LegacyFakeTimers

Verified sample for npm @jest/fake-timers 29.7.0: LegacyFakeTimers. The contract ran on node 22 · linux alpine/x64 · docker and passed.

sha256:c6a1af5594858c37f532883ff6636bbc0a1d78dad55a7b2a768c7772880b60f7

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
1
Signing keys that built it
1
Declared environment node 22.23 linux 24 · ubuntu · glibc 2.39 x64 node 22.23 javascript npm 10

Verification-run environments

Environment Contract Stages Run
node 22 · linux alpine/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22-alpine@sha256:c610fcdfb1d5…		 2026-08-26

Case

HOW
Goal
verify LegacyFakeTimers in pkg:npm/%40jest/fake-timers@29.7.0
Packages
Symbols
  • LegacyFakeTimers
Environment
node 22.23.2
Created
2026-08-26T04:22:58Z

Contract

  1. LegacyFakeTimers installs fake timer mocks onto the target global object with useFakeTimers
  2. LegacyFakeTimers tracks and reports pending timer counts via getTimerCount
  3. LegacyFakeTimers advances virtual time and triggers timer callbacks via advanceTimersByTime
  4. LegacyFakeTimers advances virtual clock to subsequent timer expiries with advanceTimersToNextTimer
  5. LegacyFakeTimers executes all queued timers, ticks, and immediates with runAllTimers
  6. LegacyFakeTimers executes only currently scheduled timers with runOnlyPendingTimers
  7. LegacyFakeTimers processes queued process.nextTick and setImmediate callbacks with runAllTicks and runAllImmediates
  8. LegacyFakeTimers cancels pending timers and resets internal clock with clearAllTimers and reset
  9. LegacyFakeTimers temporarily executes synchronous callback with real timers using runWithRealTimers
  10. LegacyFakeTimers cleans up timers and marks instance disposed with dispose and restores original functions with useRealTimers

Files

  • PROMPT.md
  • csx.json
  • index.js
  • package-lock.json
  • package.json
  • spec.json
  • test/contract.js

Download the source artifact (tar.gz)

Source

PROMPT.md
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 LegacyFakeTimers in pkg:npm/%40jest/fake-timers@29.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40jest/fake-timers@29.7.0
Demonstrate these symbols/APIs:
  - LegacyFakeTimers
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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.
csx.json
{"case":{"caseId":"case:sha256:eee57062291eb9590558a737e1f0763bb97bd150ade748758bc48ac095fec582","constraints":{"executionContext":"node"},"contract":["LegacyFakeTimers installs fake timer mocks onto the target global object with useFakeTimers","LegacyFakeTimers tracks and reports pending timer counts via getTimerCount","LegacyFakeTimers advances virtual time and triggers timer callbacks via advanceTimersByTime","LegacyFakeTimers advances virtual clock to subsequent timer expiries with advanceTimersToNextTimer","LegacyFakeTimers executes all queued timers, ticks, and immediates with runAllTimers","LegacyFakeTimers executes only currently scheduled timers with runOnlyPendingTimers","LegacyFakeTimers processes queued process.nextTick and setImmediate callbacks with runAllTicks and runAllImmediates","LegacyFakeTimers cancels pending timers and resets internal clock with clearAllTimers and reset","LegacyFakeTimers temporarily executes synchronous callback with real timers using runWithRealTimers","LegacyFakeTimers cleans up timers and marks instance disposed with dispose and restores original functions with useRealTimers"],"goal":"verify LegacyFakeTimers in pkg:npm/%40jest/fake-timers@29.7.0","kind":"HOW","packages":["pkg:npm/%40jest/fake-timers@29.7.0"],"schemaVersion":1,"symbols":["LegacyFakeTimers"]},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","executionContext":"node","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"cjs","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40jest/fake-timers@29.7.0"],"schemaVersion":1,"subject":"pkg:npm/%40jest/fake-timers@29.7.0","symbols":["LegacyFakeTimers"],"verifierAdapter":"node-typescript@1"}
index.js
'use strict';

const { LegacyFakeTimers, ModernFakeTimers } = require('@jest/fake-timers');

/**
 * Helper to create and initialize a LegacyFakeTimers instance with a mock environment.
 */
function createLegacyFakeTimers(customGlobal = {}, customOptions = {}) {
  const targetGlobal = {
    clearImmediate: globalThis.clearImmediate,
    clearInterval: globalThis.clearInterval,
    clearTimeout: globalThis.clearTimeout,
    setImmediate: globalThis.setImmediate,
    setInterval: globalThis.setInterval,
    setTimeout: globalThis.setTimeout,
    process: { nextTick: process.nextTick },
    console: console,
    ...customGlobal
  };

  const moduleMocker = {
    fn: (impl) => {
      const mockFn = (...args) => impl(...args);
      return mockFn;
    }
  };

  const timerConfig = {
    idToRef: (id) => id,
    refToId: (ref) => ref
  };

  const config = { rootDir: '/' };

  const timers = new LegacyFakeTimers({
    global: targetGlobal,
    moduleMocker,
    timerConfig,
    config,
    ...customOptions
  });

  return { timers, global: targetGlobal };
}

module.exports = {
  LegacyFakeTimers,
  ModernFakeTimers,
  createLegacyFakeTimers
};
package-lock.json
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package.json
{
  "name": "sample-jest-fake-timers-legacy",
  "version": "1.0.0",
  "private": true,
  "description": "verify LegacyFakeTimers in pkg:npm/%40jest/fake-timers@29.7.0",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "@jest/fake-timers": "29.7.0"
  },
  "license": "MIT-0"
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify LegacyFakeTimers in pkg:npm/%40jest/fake-timers@29.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40jest/fake-timers@29.7.0"
  ],
  "symbols": [
    "LegacyFakeTimers"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}
test/contract.js
'use strict';

const assert = require('assert');
const { LegacyFakeTimers, createLegacyFakeTimers } = require('../index.js');

function testUseFakeTimersAndMockReplacement() {
  const { timers, global } = createLegacyFakeTimers();
  const originalSetTimeout = global.setTimeout;
  const originalClearTimeout = global.clearTimeout;

  timers.useFakeTimers();

  assert.notStrictEqual(global.setTimeout, originalSetTimeout);
  assert.notStrictEqual(global.clearTimeout, originalClearTimeout);
  assert.strictEqual(typeof global.setTimeout, 'function');
  assert.strictEqual(typeof global.setInterval, 'function');
  assert.strictEqual(typeof global.setImmediate, 'function');
  assert.strictEqual(typeof global.clearImmediate, 'function');
  assert.strictEqual(typeof global.clearInterval, 'function');
  assert.strictEqual(typeof global.clearTimeout, 'function');
  assert.strictEqual(typeof global.process.nextTick, 'function');

  timers.useRealTimers();
  assert.strictEqual(global.setTimeout, originalSetTimeout);
  assert.strictEqual(global.clearTimeout, originalClearTimeout);
}

function testTimerCountAndVirtualClock() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  assert.strictEqual(timers.now(), 0);
  assert.strictEqual(timers.getTimerCount(), 0);

  global.setTimeout(() => {}, 100);
  global.setInterval(() => {}, 200);
  global.setImmediate(() => {});
  global.process.nextTick(() => {});

  assert.strictEqual(timers.getTimerCount(), 4);

  timers.useRealTimers();
}

function testAdvanceTimersByTime() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  const executionLog = [];

  global.setTimeout((arg) => {
    executionLog.push(`timeout-100:${arg}`);
  }, 100, 'first');

  global.setTimeout((arg) => {
    executionLog.push(`timeout-250:${arg}`);
  }, 250, 'second');

  global.setInterval(() => {
    executionLog.push('interval-100');
  }, 100);

  timers.advanceTimersByTime(150);
  assert.strictEqual(timers.now(), 150);
  assert.deepStrictEqual(executionLog, ['timeout-100:first', 'interval-100']);

  timers.advanceTimersByTime(150);
  assert.strictEqual(timers.now(), 300);
  assert.deepStrictEqual(executionLog, [
    'timeout-100:first',
    'interval-100',
    'interval-100',
    'timeout-250:second',
    'interval-100'
  ]);

  timers.useRealTimers();
}

function testAdvanceTimersToNextTimer() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  const executed = [];
  global.setTimeout(() => executed.push(50), 50);
  global.setTimeout(() => executed.push(120), 120);
  global.setTimeout(() => executed.push(300), 300);

  timers.advanceTimersToNextTimer(1);
  assert.strictEqual(timers.now(), 50);
  assert.deepStrictEqual(executed, [50]);

  timers.advanceTimersToNextTimer(2);
  assert.strictEqual(timers.now(), 300);
  assert.deepStrictEqual(executed, [50, 120, 300]);

  timers.useRealTimers();
}

function testRunAllTimers() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  const results = [];
  global.setTimeout(() => {
    results.push('t1');
    global.setTimeout(() => {
      results.push('t2');
    }, 50);
  }, 50);

  global.setImmediate(() => {
    results.push('imm1');
  });

  global.process.nextTick(() => {
    results.push('tick1');
  });

  timers.runAllTimers();
  assert.deepStrictEqual(results, ['tick1', 'imm1', 't1', 't2']);
  assert.strictEqual(timers.getTimerCount(), 0);

  timers.useRealTimers();
}

function testRunOnlyPendingTimers() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  const executed = [];
  global.setTimeout(() => {
    executed.push('pending1');
    global.setTimeout(() => {
      executed.push('nested1');
    }, 10);
  }, 100);

  global.setTimeout(() => {
    executed.push('pending2');
  }, 200);

  timers.runOnlyPendingTimers();
  assert.deepStrictEqual(executed, ['pending1', 'pending2']);
  assert.strictEqual(timers.getTimerCount(), 1);

  timers.advanceTimersByTime(10);
  assert.deepStrictEqual(executed, ['pending1', 'pending2', 'nested1']);
  assert.strictEqual(timers.getTimerCount(), 0);

  timers.useRealTimers();
}

function testRunAllTicksAndImmediates() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  const tickResults = [];
  const immediateResults = [];

  global.process.nextTick(() => tickResults.push('tick-a'));
  global.process.nextTick(() => tickResults.push('tick-b'));
  global.setImmediate(() => immediateResults.push('imm-a'));
  global.setImmediate(() => immediateResults.push('imm-b'));

  assert.strictEqual(timers.getTimerCount(), 4);

  timers.runAllTicks();
  assert.deepStrictEqual(tickResults, ['tick-a', 'tick-b']);
  assert.strictEqual(immediateResults.length, 0);

  timers.runAllImmediates();
  assert.deepStrictEqual(immediateResults, ['imm-a', 'imm-b']);
  assert.strictEqual(timers.getTimerCount(), 0);

  timers.useRealTimers();
}

function testClearAllTimersAndReset() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  let executed = false;
  global.setTimeout(() => {
    executed = true;
  }, 100);

  global.setImmediate(() => {
    executed = true;
  });

  assert.strictEqual(timers.getTimerCount(), 2);
  timers.clearAllTimers();
  assert.strictEqual(timers.getTimerCount(), 0);

  timers.advanceTimersByTime(500);
  assert.strictEqual(executed, false);

  global.setTimeout(() => {}, 200);
  timers.advanceTimersByTime(100);
  assert.strictEqual(timers.now(), 600);

  timers.reset();
  assert.strictEqual(timers.now(), 0);
  assert.strictEqual(timers.getTimerCount(), 0);

  timers.useRealTimers();
}

function testRunWithRealTimers() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  const fakeSetTimeout = global.setTimeout;
  let executedSynchronously = false;

  timers.runWithRealTimers(() => {
    assert.notStrictEqual(global.setTimeout, fakeSetTimeout);
    executedSynchronously = true;
  });

  assert.strictEqual(executedSynchronously, true);
  assert.strictEqual(global.setTimeout, fakeSetTimeout);

  timers.useRealTimers();
}

function testDispose() {
  const { timers, global } = createLegacyFakeTimers();
  timers.useFakeTimers();

  let ran = false;
  global.setTimeout(() => {
    ran = true;
  }, 100);

  timers.dispose();
  assert.strictEqual(timers.getTimerCount(), 0);

  // Calling timer APIs after dispose should return null / noop
  const timerHandle = global.setTimeout(() => {}, 100);
  assert.strictEqual(timerHandle, null);

  timers.useRealTimers();
}

function runAll() {
  testUseFakeTimersAndMockReplacement();
  testTimerCountAndVirtualClock();
  testAdvanceTimersByTime();
  testAdvanceTimersToNextTimer();
  testRunAllTimers();
  testRunOnlyPendingTimers();
  testRunAllTicksAndImmediates();
  testClearAllTimersAndReset();
  testRunWithRealTimers();
  testDispose();

  console.log('All LegacyFakeTimers contract assertions passed successfully.');
}

runAll();

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