CodeSampleX

Sample

@jest/console 30.4.1: BufferedConsole, CustomConsole, NullConsole

Verified sample for npm @jest/console 30.4.1: BufferedConsole, CustomConsole, NullConsole. The contract ran on node 22 · linux alpine/x64 · docker and passed.

sha256:83643f40443a66f5cd8a550b0d571c0dc5e3b2e7383a2936f66d370b44a8ed1d

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…		 2026-08-27

Case

HOW
Goal
verify pkg:npm/%40jest/console@30.4.1
Packages
Symbols
  • BufferedConsole
  • CustomConsole
  • NullConsole
  • getConsoleOutput
Environment
node 22.23.2
Created
2026-08-27T22:38:50Z

Contract

  1. BufferedConsole captures log, info, warn, error, and debug messages into an in-memory buffer with type, message, and caller origin stack trace
  2. BufferedConsole.write appends structured log entries directly to a target buffer array
  3. BufferedConsole manages indentation levels for grouped logs with group and groupCollapsed while groupEnd resets indentation without creating buffer entries
  4. BufferedConsole tracks named timers with time and timeEnd and named counters with count and countReset
  5. BufferedConsole.assert logs an AssertionError entry with type assert when evaluated condition is falsy and ignores truthy conditions
  6. getConsoleOutput formats buffered console log entries into indented output strings with colorized log types and stack traces
  7. captureConsoleLogs intercepts global console output during function execution and restores the original global console on completion
  8. CustomConsole writes console entries directly to custom writable stdout and stderr streams
  9. NullConsole requires writable streams in constructor and silences all console output without throwing

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 pkg:npm/%40jest/console@30.4.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/%40jest/console@30.4.1
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:sha256:073421ee5ed707086806fc42894c3b047ad70c4e9aabfdfe55fdd974f2eb0c13","constraints":{"executionContext":"node"},"contract":["BufferedConsole captures log, info, warn, error, and debug messages into an in-memory buffer with type, message, and caller origin stack trace","BufferedConsole.write appends structured log entries directly to a target buffer array","BufferedConsole manages indentation levels for grouped logs with group and groupCollapsed while groupEnd resets indentation without creating buffer entries","BufferedConsole tracks named timers with time and timeEnd and named counters with count and countReset","BufferedConsole.assert logs an AssertionError entry with type assert when evaluated condition is falsy and ignores truthy conditions","getConsoleOutput formats buffered console log entries into indented output strings with colorized log types and stack traces","captureConsoleLogs intercepts global console output during function execution and restores the original global console on completion","CustomConsole writes console entries directly to custom writable stdout and stderr streams","NullConsole requires writable streams in constructor and silences all console output without throwing"],"goal":"verify pkg:npm/%40jest/console@30.4.1","kind":"HOW","packages":["pkg:npm/%40jest/console@30.4.1"],"schemaVersion":1,"symbols":["BufferedConsole","CustomConsole","NullConsole","getConsoleOutput"]},"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/console@30.4.1"],"schemaVersion":1,"subject":"pkg:npm/%40jest/console@30.4.1","symbols":["BufferedConsole","CustomConsole","NullConsole","getConsoleOutput"],"verifierAdapter":"node-typescript@1"}
index.js
'use strict';

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

/**
 * Creates a new BufferedConsole instance.
 * @param {Function} [getSourceMaps] - Optional source map resolver function.
 * @returns {BufferedConsole}
 */
function createBufferedConsole(getSourceMaps = () => null) {
  return new BufferedConsole(getSourceMaps);
}

/**
 * Formats a console buffer using getConsoleOutput with given options.
 * @param {Array<object>} buffer - Log entries buffer from BufferedConsole.
 * @param {object} [options] - Configuration options.
 * @param {string} [options.rootDir] - Root directory for stack trace normalization.
 * @param {boolean} [options.verbose] - Whether to use verbose indentation.
 * @param {boolean} [options.noStackTrace] - Whether to omit stack traces.
 * @returns {string} Formatted console output string.
 */
function formatConsoleEntries(buffer, options = {}) {
  const rootDir = options.rootDir || process.cwd();
  const config = { rootDir };
  const globalConfig = {
    verbose: Boolean(options.verbose),
    noStackTrace: Boolean(options.noStackTrace)
  };
  return getConsoleOutput(buffer, config, globalConfig);
}

/**
 * Executes a callback function and captures all console messages logged during its execution.
 * @param {Function} fn - Function to execute.
 * @param {object} [formatOptions] - Options passed to formatConsoleEntries.
 * @returns {{ result: *, buffer: Array<object>, output: string, console: BufferedConsole }}
 */
function captureConsoleLogs(fn, formatOptions = {}) {
  const bufferedConsole = createBufferedConsole();
  const originalConsole = global.console;
  let result;

  try {
    global.console = bufferedConsole;
    result = fn(bufferedConsole);
  } finally {
    global.console = originalConsole;
  }

  const buffer = bufferedConsole.getBuffer() || [];
  const output = formatConsoleEntries(buffer, formatOptions);

  return {
    result,
    buffer,
    output,
    console: bufferedConsole
  };
}

/**
 * Creates a CustomConsole that writes output through custom writable streams.
 * @param {NodeJS.WritableStream} stdout - Stream for stdout messages (log, info, dir, etc.).
 * @param {NodeJS.WritableStream} stderr - Stream for stderr messages (warn, error, assert).
 * @param {Function} [formatBuffer] - Optional custom buffer formatter function.
 * @returns {CustomConsole}
 */
function createCustomConsole(stdout, stderr, formatBuffer) {
  return new CustomConsole(stdout, stderr, formatBuffer);
}

/**
 * Creates a NullConsole instance with default no-op streams if none provided.
 * @param {NodeJS.WritableStream} [stdout] - Optional stdout stream.
 * @param {NodeJS.WritableStream} [stderr] - Optional stderr stream.
 * @returns {NullConsole}
 */
function createNullConsole(stdout, stderr) {
  const devNull = () =>
    new Writable({
      write(chunk, encoding, callback) {
        callback();
      }
    });
  return new NullConsole(stdout || devNull(), stderr || devNull());
}

module.exports = {
  BufferedConsole,
  CustomConsole,
  NullConsole,
  getConsoleOutput,
  createBufferedConsole,
  formatConsoleEntries,
  captureConsoleLogs,
  createCustomConsole,
  createNullConsole
};
package-lock.json
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      "license": "MIT",
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      "license": "MIT"
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}
package.json
{
  "name": "sample-jest-console",
  "version": "1.0.0",
  "private": true,
  "description": "verify pkg:npm/%40jest/console@30.4.1",
  "main": "index.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "@jest/console": "30.4.1"
  },
  "license": "MIT-0"
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/%40jest/console@30.4.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/%40jest/console@30.4.1"
  ],
  "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 { Writable } = require('stream');
const {
  BufferedConsole,
  CustomConsole,
  NullConsole,
  getConsoleOutput,
  createBufferedConsole,
  formatConsoleEntries,
  captureConsoleLogs,
  createCustomConsole,
  createNullConsole
} = require('../index.js');

function testBufferedConsoleLogging() {
  const consoleInstance = createBufferedConsole();
  consoleInstance.log('standard log message');
  consoleInstance.info('informational notice');
  consoleInstance.warn('warning notice');
  consoleInstance.error('error event');
  consoleInstance.debug('debug trace');

  const buffer = consoleInstance.getBuffer();
  assert.ok(Array.isArray(buffer), 'buffer must be an array');
  assert.strictEqual(buffer.length, 5, 'buffer must contain exactly 5 entries');

  assert.strictEqual(buffer[0].type, 'log');
  assert.strictEqual(buffer[0].message, 'standard log message');
  assert.ok(typeof buffer[0].origin === 'string' && buffer[0].origin.length > 0);

  assert.strictEqual(buffer[1].type, 'info');
  assert.strictEqual(buffer[1].message, 'informational notice');

  assert.strictEqual(buffer[2].type, 'warn');
  assert.strictEqual(buffer[2].message, 'warning notice');

  assert.strictEqual(buffer[3].type, 'error');
  assert.strictEqual(buffer[3].message, 'error event');

  assert.strictEqual(buffer[4].type, 'debug');
  assert.strictEqual(buffer[4].message, 'debug trace');
}

function testBufferedConsoleStaticWrite() {
  const targetBuffer = [];
  BufferedConsole.write(targetBuffer, 'warn', 'manually written message', 1);

  assert.strictEqual(targetBuffer.length, 1);
  assert.strictEqual(targetBuffer[0].type, 'warn');
  assert.strictEqual(targetBuffer[0].message, 'manually written message');
  assert.ok(typeof targetBuffer[0].origin === 'string');
}

function testBufferedConsoleGrouping() {
  const consoleInstance = createBufferedConsole();
  consoleInstance.group('Parent Group');
  consoleInstance.log('nested item 1');
  consoleInstance.groupCollapsed('Child Group');
  consoleInstance.log('deeply nested item');
  consoleInstance.groupEnd();
  consoleInstance.log('nested item 2');
  consoleInstance.groupEnd();

  const buffer = consoleInstance.getBuffer();
  assert.strictEqual(buffer.length, 5);

  assert.strictEqual(buffer[0].type, 'group');
  assert.strictEqual(buffer[0].message, '  Parent Group');

  assert.strictEqual(buffer[1].type, 'log');
  assert.strictEqual(buffer[1].message, '  nested item 1');

  assert.strictEqual(buffer[2].type, 'groupCollapsed');
  assert.strictEqual(buffer[2].message, '    Child Group');

  assert.strictEqual(buffer[3].type, 'log');
  assert.strictEqual(buffer[3].message, '    deeply nested item');

  assert.strictEqual(buffer[4].type, 'log');
  assert.strictEqual(buffer[4].message, '  nested item 2');
}

function testBufferedConsoleTimersAndCounters() {
  const consoleInstance = createBufferedConsole();
  consoleInstance.count('testCounter');
  consoleInstance.count('testCounter');
  consoleInstance.countReset('testCounter');
  consoleInstance.count('testCounter');

  consoleInstance.time('operationTimer');
  consoleInstance.timeEnd('operationTimer');

  const buffer = consoleInstance.getBuffer();
  assert.strictEqual(buffer[0].message, 'testCounter: 1');
  assert.strictEqual(buffer[1].message, 'testCounter: 2');
  assert.strictEqual(buffer[2].message, 'testCounter: 1');

  assert.strictEqual(buffer[3].type, 'time');
  assert.match(buffer[3].message, /^operationTimer: \d+(\.\d+)?\s*(ms|s)$/);
}

function testBufferedConsoleAssertions() {
  const consoleInstance = createBufferedConsole();
  consoleInstance.assert(true, 'truthy condition must not log');
  assert.strictEqual(consoleInstance.getBuffer(), undefined);

  consoleInstance.assert(false, 'falsy condition logged');
  const buffer = consoleInstance.getBuffer();
  assert.strictEqual(buffer.length, 1);
  assert.strictEqual(buffer[0].type, 'assert');
  assert.match(buffer[0].message, /AssertionError.*falsy condition logged/);
}

function testGetConsoleOutputFormatting() {
  const consoleInstance = createBufferedConsole();
  consoleInstance.log('output formatting log');
  consoleInstance.warn('output formatting warn');
  consoleInstance.error('output formatting error');

  const buffer = consoleInstance.getBuffer();
  const formattedVerbose = formatConsoleEntries(buffer, {
    verbose: true,
    noStackTrace: false
  });
  assert.match(formattedVerbose, /console\.log/);
  assert.match(formattedVerbose, /output formatting log/);
  assert.match(formattedVerbose, /console\.warn/);
  assert.match(formattedVerbose, /output formatting warn/);
  assert.match(formattedVerbose, /console\.error/);
  assert.match(formattedVerbose, /output formatting error/);

  const formattedNoStack = formatConsoleEntries(buffer, {
    verbose: false,
    noStackTrace: true
  });
  assert.match(formattedNoStack, /output formatting log/);
}

function testCaptureConsoleLogs() {
  const result = captureConsoleLogs(() => {
    console.log('intercepted message');
    console.warn('intercepted warning');
    return 'success-value';
  });

  assert.strictEqual(result.result, 'success-value');
  assert.strictEqual(result.buffer.length, 2);
  assert.strictEqual(result.buffer[0].message, 'intercepted message');
  assert.strictEqual(result.buffer[1].message, 'intercepted warning');
  assert.match(result.output, /intercepted message/);
}

function testCustomConsoleStreaming() {
  const stdoutChunks = [];
  const stderrChunks = [];

  const stdoutStream = new Writable({
    write(chunk, encoding, callback) {
      stdoutChunks.push(chunk.toString());
      callback();
    }
  });

  const stderrStream = new Writable({
    write(chunk, encoding, callback) {
      stderrChunks.push(chunk.toString());
      callback();
    }
  });

  const customConsole = createCustomConsole(stdoutStream, stderrStream);
  customConsole.log('stdout message');
  customConsole.error('stderr message');

  assert.strictEqual(stdoutChunks.join(''), 'stdout message\n');
  assert.strictEqual(stderrChunks.join(''), 'stderr message\n');
}

function testNullConsole() {
  assert.throws(
    () => {
      new NullConsole();
    },
    (err) => {
      assert.strictEqual(err.code, 'ERR_CONSOLE_WRITABLE_STREAM');
      return true;
    }
  );

  const nullConsole = createNullConsole();
  nullConsole.log('silenced log');
  nullConsole.info('silenced info');
  nullConsole.warn('silenced warn');
  nullConsole.error('silenced error');
  nullConsole.debug('silenced debug');
}

function runAll() {
  testBufferedConsoleLogging();
  testBufferedConsoleStaticWrite();
  testBufferedConsoleGrouping();
  testBufferedConsoleTimersAndCounters();
  testBufferedConsoleAssertions();
  testGetConsoleOutputFormatting();
  testCaptureConsoleLogs();
  testCustomConsoleStreaming();
  testNullConsole();

  console.log('Contract tests passed successfully.');
  process.exit(0);
}

runAll();

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