CodeSampleX

Sample

@jest/console 29.7.0: NullConsole

Verified sample for npm @jest/console 29.7.0: NullConsole. The contract ran on node 22 · linux alpine/x64 · docker and passed.

sha256:c293b57a2933bf1728696545a605eb0964eab66e23c3f7729ba82689cfb821b7

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 linux 24 · ubuntu · glibc 2.39 x64 npm

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…		 2026-08-27

Case

HOW
Goal
verify @jest/console.NullConsole in pkg:npm/%40jest/console@29.7.0
Packages
Symbols
  • @jest/console.NullConsole
Created
2026-08-27T18:02:08Z

Contract

  1. NullConsole constructor requires writable stream instances for stdout and stderr or throws ERR_CONSOLE_WRITABLE_STREAM
  2. createNullConsole creates a NullConsole instance with default no-op writable streams
  3. NullConsole suppresses log, info, warn, error, and debug messages without writing to output streams
  4. NullConsole assert, dir, and trace methods execute as no-ops without throwing errors
  5. NullConsole group, groupCollapsed, and groupEnd manage indentation state silently without writing output
  6. NullConsole time, timeEnd, timeLog, count, and countReset execute silently without logging
  7. withNullConsole temporarily silences global console output during function execution and restores the original console

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 @jest/console.NullConsole in pkg:npm/%40jest/console@29.7.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40jest/console@29.7.0
Demonstrate these symbols/APIs:
  - @jest/console.NullConsole

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:b97b06c9d24dca19ee00f760c68d3830b7bd13ece52e422daeca4ffa1faf36a0","contract":["NullConsole constructor requires writable stream instances for stdout and stderr or throws ERR_CONSOLE_WRITABLE_STREAM","createNullConsole creates a NullConsole instance with default no-op writable streams","NullConsole suppresses log, info, warn, error, and debug messages without writing to output streams","NullConsole assert, dir, and trace methods execute as no-ops without throwing errors","NullConsole group, groupCollapsed, and groupEnd manage indentation state silently without writing output","NullConsole time, timeEnd, timeLog, count, and countReset execute silently without logging","withNullConsole temporarily silences global console output during function execution and restores the original console"],"goal":"verify @jest/console.NullConsole in pkg:npm/%40jest/console@29.7.0","kind":"HOW","packages":["pkg:npm/%40jest/console@29.7.0"],"schemaVersion":1,"symbols":["@jest/console.NullConsole"]},"contractCommand":["node","test/contract.js"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/%40jest/console@29.7.0"],"schemaVersion":1,"subject":"pkg:npm/%40jest/console@29.7.0","symbols":["@jest/console.NullConsole"],"verifierAdapter":"node-typescript@1"}
index.js
'use strict';

const { Writable } = require('stream');
const { NullConsole } = require('@jest/console');

/**
 * Creates a no-op writable stream that discards all written data.
 * @returns {Writable} A no-op writable stream.
 */
function createNullStream() {
  return new Writable({
    write(_chunk, _encoding, callback) {
      callback();
    }
  });
}

/**
 * Creates a NullConsole instance initialized with no-op writable streams.
 * If custom stdout or stderr streams are provided, they are forwarded to the constructor.
 *
 * @param {Writable} [stdout] - Optional stdout stream (defaults to no-op writable stream).
 * @param {Writable} [stderr] - Optional stderr stream (defaults to no-op writable stream).
 * @param {Function} [formatBuffer] - Optional formatBuffer transformer function.
 * @returns {NullConsole} A configured NullConsole instance.
 */
function createNullConsole(
  stdout = createNullStream(),
  stderr = createNullStream(),
  formatBuffer = (_type, message) => message
) {
  return new NullConsole(stdout, stderr, formatBuffer);
}

/**
 * Executes a function with global.console temporarily replaced by a NullConsole,
 * suppressing any console logs generated during the function's execution.
 * Restores the original global.console afterwards.
 *
 * @param {Function} fn - Synchronous or async function to execute in silenced mode.
 * @returns {*} The return value of fn.
 */
function withNullConsole(fn) {
  const nullConsole = createNullConsole();
  const originalConsole = global.console;
  try {
    global.console = nullConsole;
    return fn(nullConsole);
  } finally {
    global.console = originalConsole;
  }
}

module.exports = {
  NullConsole,
  createNullStream,
  createNullConsole,
  withNullConsole
};
package-lock.json
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package.json
{
  "name": "sample-jest-console-null",
  "version": "1.0.0",
  "private": true,
  "description": "verify @jest/console.NullConsole in pkg:npm/%40jest/console@29.7.0",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "@jest/console": "29.7.0"
  },
  "license": "MIT-0"
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify @jest/console.NullConsole in pkg:npm/%40jest/console@29.7.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40jest/console@29.7.0"
  ],
  "symbols": [
    "@jest/console.NullConsole"
  ]
}
test/contract.js
'use strict';

const assert = require('assert');
const { Writable } = require('stream');
const {
  NullConsole,
  createNullStream,
  createNullConsole,
  withNullConsole
} = require('../index.js');

function testNullConsoleDirectInstantiation() {
  assert.throws(
    () => new NullConsole(),
    (err) => {
      return (
        err instanceof TypeError &&
        err.code === 'ERR_CONSOLE_WRITABLE_STREAM'
      );
    },
    'new NullConsole() without streams should throw ERR_CONSOLE_WRITABLE_STREAM'
  );

  let streamWrites = 0;
  const customStream = new Writable({
    write(_chunk, _encoding, callback) {
      streamWrites++;
      callback();
    }
  });

  const nc = new NullConsole(customStream, customStream);
  assert.ok(nc instanceof NullConsole, 'nc should be an instance of NullConsole');
  assert.strictEqual(nc.getBuffer(), undefined, 'NullConsole.getBuffer() should be undefined');
  assert.strictEqual(streamWrites, 0, 'No stream writes on instantiation');
}

function testCreateNullConsoleHelper() {
  const nc = createNullConsole();
  assert.ok(nc instanceof NullConsole, 'createNullConsole should return a NullConsole instance');
  assert.strictEqual(nc.getBuffer(), undefined, 'getBuffer should return undefined');
}

function testNullConsoleSuppressesOutput() {
  let writes = 0;
  const trackingStream = new Writable({
    write(_chunk, _encoding, callback) {
      writes++;
      callback();
    }
  });

  const nc = createNullConsole(trackingStream, trackingStream);

  nc.log('sample log message %s', 'formatted');
  nc.info('sample info message');
  nc.warn('sample warn message');
  nc.error('sample error message');
  nc.debug('sample debug message');

  assert.strictEqual(writes, 0, 'Logging methods must not write to streams');
}

function testNullConsoleNoOpMethods() {
  const nc = createNullConsole();

  assert.doesNotThrow(() => {
    nc.assert(false, 'this assertion should be ignored');
    nc.assert(true, 'truthy assertion');
  });

  assert.doesNotThrow(() => {
    nc.dir({ key: 'value', nested: [1, 2, 3] });
    nc.trace('sample trace');
  });
}

function testNullConsoleGrouping() {
  const nc = createNullConsole();

  assert.doesNotThrow(() => {
    nc.group('Group Level 1');
    nc.log('Grouped log 1');
    nc.groupCollapsed('Group Level 2');
    nc.log('Grouped log 2');
    nc.groupEnd();
    nc.groupEnd();
  });
}

function testNullConsoleTimingAndCounting() {
  const nc = createNullConsole();

  assert.doesNotThrow(() => {
    nc.time('benchmark-timer');
    nc.timeLog('benchmark-timer', 'checkpoint');
    nc.timeEnd('benchmark-timer');

    nc.count('counter');
    nc.count('counter');
    nc.countReset('counter');
  });
}

function testWithNullConsoleExecution() {
  let innerLogCalled = false;
  const originalConsole = global.console;

  const result = withNullConsole((silencedConsole) => {
    assert.ok(silencedConsole instanceof NullConsole);
    assert.strictEqual(global.console, silencedConsole);

    console.log('This log should be completely silenced');
    console.error('This error should be completely silenced');
    innerLogCalled = true;
    return 100;
  });

  assert.strictEqual(result, 100, 'withNullConsole returns inner function result');
  assert.strictEqual(innerLogCalled, true, 'inner function executed');
  assert.strictEqual(global.console, originalConsole, 'global.console restored after execution');
}

function testWithNullConsoleExceptionSafety() {
  const originalConsole = global.console;

  assert.throws(
    () => {
      withNullConsole(() => {
        throw new Error('Test error inside withNullConsole');
      });
    },
    /Test error inside withNullConsole/
  );

  assert.strictEqual(global.console, originalConsole, 'global.console restored even on exception');
}

function main() {
  testNullConsoleDirectInstantiation();
  testCreateNullConsoleHelper();
  testNullConsoleSuppressesOutput();
  testNullConsoleNoOpMethods();
  testNullConsoleGrouping();
  testNullConsoleTimingAndCounting();
  testWithNullConsoleExecution();
  testWithNullConsoleExceptionSafety();
  console.log('All @jest/console.NullConsole contract tests passed successfully.');
}

main();

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