mimic-response 3.1.0

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/mimic-response@3.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/mimic-response@3.1.0
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.

{"case":{"caseId":"case:sha256:9494774e3352fab876617a927d6de6d38871d5f3bdf9016c1ddc3a68a578aa8b","constraints":{"executionContext":"node"},"contract":["mimicResponse(fromStream, toStream) copies HTTP response properties including statusCode, statusMessage, headers, and url from fromStream to toStream","mimicResponse(fromStream, toStream) returns the destination toStream instance","mimicResponse(fromStream, toStream) does not overwrite properties already existing on toStream","mimicResponse(fromStream, toStream) throws an Error if toStream has autoDestroy enabled","mimicResponse(fromStream, toStream) forwards getters and setters between fromStream and toStream","mimicResponse(fromStream, toStream) propagates aborted event from fromStream to destroy toStream"],"goal":"verify pkg:npm/mimic-response@3.1.0","kind":"HOW","packages":["pkg:npm/mimic-response@3.1.0"],"schemaVersion":1},"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/mimic-response@3.1.0"],"schemaVersion":1,"subject":"pkg:npm/mimic-response@3.1.0","verifierAdapter":"node-typescript@1"}

{
  "name": "csx-sample-mimic-response",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "csx-sample-mimic-response",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "mimic-response": "3.1.0"
      }
    },
    "node_modules/mimic-response": {
      "version": "3.1.0",
      "resolved": "https://registry.npmjs.org/mimic-response/-/mimic-response-3.1.0.tgz",
      "integrity": "sha512-z0yWI+4FDrrweS8Zmt4Ej5HdJmky15+L2e6Wgn3+iK5fWzb6T3fhNFq2+MeTRb064c6Wr4N/wv0DzQTjNzHNGQ==",
      "license": "MIT",
      "engines": {
        "node": ">=10"
      }
    }
  }
}

{
  "name": "csx-sample-mimic-response",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for mimic-response",
  "main": "test/contract.js",
  "scripts": {
    "test": "node test/contract.js"
  },
  "dependencies": {
    "mimic-response": "3.1.0"
  },
  "license": "MIT-0"
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/mimic-response@3.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/mimic-response@3.1.0"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

const assert = require('assert');
const { PassThrough } = require('stream');
const mimicResponse = require('mimic-response');

async function runTests() {
  // Test 1: Copies HTTP response properties and returns toStream
  {
    const fromStream = new PassThrough();
    fromStream.statusCode = 200;
    fromStream.statusMessage = 'OK';
    fromStream.headers = { 'content-type': 'application/json' };
    fromStream.httpVersion = '1.1';
    fromStream.url = '/api/resource';
    fromStream.method = 'GET';

    const toStream = new PassThrough({ autoDestroy: false });
    const result = mimicResponse(fromStream, toStream);

    assert.strictEqual(result, toStream, 'mimicResponse should return toStream');
    assert.strictEqual(toStream.statusCode, 200, 'statusCode should match');
    assert.strictEqual(toStream.statusMessage, 'OK', 'statusMessage should match');
    assert.deepStrictEqual(toStream.headers, { 'content-type': 'application/json' }, 'headers should match');
    assert.strictEqual(toStream.httpVersion, '1.1', 'httpVersion should match');
    assert.strictEqual(toStream.url, '/api/resource', 'url should match');
    assert.strictEqual(toStream.method, 'GET', 'method should match');
  }

  // Test 2: Does not overwrite existing properties on toStream
  {
    const fromStream = new PassThrough();
    fromStream.statusCode = 200;
    fromStream.customProperty = 'from-source';

    const toStream = new PassThrough({ autoDestroy: false });
    toStream.customProperty = 'original-destination';

    mimicResponse(fromStream, toStream);
    assert.strictEqual(toStream.customProperty, 'original-destination', 'existing property should not be overwritten');
    assert.strictEqual(toStream.statusCode, 200, 'new property should be copied');
  }

  // Test 3: Throws an Error if toStream has autoDestroy enabled
  {
    const fromStream = new PassThrough();
    const toStream = new PassThrough({ autoDestroy: true });

    assert.throws(
      () => mimicResponse(fromStream, toStream),
      /The second stream must have the `autoDestroy` option set to `false`/,
      'should throw error when autoDestroy is true'
    );
  }

  // Test 4: Forwards getters and setters between fromStream and toStream
  {
    const fromStream = new PassThrough();
    fromStream.statusCode = 200;

    const toStream = new PassThrough({ autoDestroy: false });
    mimicResponse(fromStream, toStream);

    toStream.statusCode = 404;
    assert.strictEqual(fromStream.statusCode, 404, 'setting property on toStream should update fromStream');

    fromStream.statusMessage = 'Not Found';
    assert.strictEqual(toStream.statusMessage, 'Not Found', 'updating property on fromStream should reflect on toStream');
  }

  // Test 5: Propagates aborted event from fromStream to destroy toStream
  await new Promise((resolve, reject) => {
    const fromStream = new PassThrough();
    const toStream = new PassThrough({ autoDestroy: false });

    mimicResponse(fromStream, toStream);

    let abortedEmitted = false;
    toStream.on('aborted', () => {
      abortedEmitted = true;
    });

    toStream.on('close', () => {
      try {
        assert.strictEqual(abortedEmitted, true, 'aborted event should have been emitted on toStream');
        assert.strictEqual(toStream.destroyed, true, 'toStream should be destroyed');
        resolve();
      } catch (err) {
        reject(err);
      }
    });

    fromStream.emit('aborted');
  });

  console.log('All mimic-response contract assertions passed successfully.');
}

runTests().catch((err) => {
  console.error('Contract test failed:', err);
  process.exit(1);
});