Node.js Legacy Mock Modules (vojtajina/node-mocks)

Common errors

• SyntaxError: Cannot use import statement outside a module

  cause Attempting to use ES Module `import` syntax with the CommonJS-only `mocks` package.
  fix Change `import mocks from 'mocks';` to `const mocks = require('mocks');` and ensure your environment supports CommonJS.

• TypeError: fs.someUnsupportedMethod is not a function

  cause Attempting to call an `fs` or `http` method that is not implemented by the `mocks` package.
  fix Consult the `mocks` package's GitHub repository for the limited list of supported methods. For broader API support, consider modern alternatives like `mock-fs` or `nock`.

• Error: Cannot find module 'mocks'

  cause The package is not installed or the Node.js runtime cannot resolve its path.
  fix Ensure the package is installed via `npm install mocks` or `yarn add mocks` and that your Node.js resolution paths are correctly configured. Verify that `node_modules` is accessible.

Warnings

• breaking The `mocks` package is officially abandoned and has not been updated since August 2013. It is not compatible with modern Node.js versions or ES Modules, and its APIs are severely outdated and incomplete compared to current Node.js built-ins.
  Fix: Migrate to actively maintained mocking libraries like `mock-fs` (for file system), `nock` or `node-mocks-http` (for HTTP), or general testing frameworks (e.g., Jest, Sinon.js) for robust and current testing solutions.
• gotcha The mock `fs` and `http` modules provided by this package implement only a very small subset of the actual Node.js APIs. Many common `fs` or `http` methods will be missing or have incomplete implementations, leading to unexpected runtime errors during testing.
  Fix: Review the source code or limited documentation on the GitHub page to understand exactly which methods are supported. For broader API coverage, consider alternative libraries.
• gotcha This package is written exclusively in CommonJS and does not provide ES Module (ESM) entry points. Attempting to `import` it will result in a `SyntaxError` in ESM contexts.
  Fix: Use CommonJS `require()` syntax (`const mocks = require('mocks');`) to import the package. If your project is ESM-only, you will need to use a different mocking library.
• gotcha There are no TypeScript type definitions available for the `mocks` package. Using it in a TypeScript project will result in type errors and lack of autocomplete, requiring manual type declarations.
  Fix: Either create custom declaration files (`.d.ts`) or, preferably, migrate to a modern mocking library that offers built-in TypeScript support.

Install

• npm install mocks npm
• yarn add mocks yarn
• pnpm add mocks pnpm

Imports

• mocks
  wrong:

  import mocks from 'mocks';

  correct:

  const mocks = require('mocks');

  This package is CommonJS-only and does not support ES Modules. Using `import` will result in a runtime error.
• mocks.fs
  wrong:

  const fs = require('fs'); // This loads the real fs module unless patched differently

  correct:

  const fs = require('mocks').fs;

  Access the mocked `fs` module directly from the `mocks` object. The package does not automatically monkey-patch the global `fs` module.
• mocks.http
  wrong:

  const http = require('http'); // This loads the real http module

  correct:

  const http = require('mocks').http;

  Access the mocked `http` module directly from the `mocks` object. It provides `ServerRequest` and `ServerResponse` constructors.

Quickstart

This quickstart demonstrates how to use the `mocks` package to set up a mock file system (using `_set` and `readFileSync`) and create mock HTTP request/response objects for basic unit testing scenarios in a legacy Node.js environment.

const mocks = require('mocks');
const fs = mocks.fs; // Get the mocked fs module
const http = mocks.http; // Get the mocked http module

// Configure the mock file system with files and directories
fs._set('/app/data/config.json', JSON.stringify({ version: '1.0.0', enabled: true }));
fs._set('/app/logs', {}); // Mock an empty directory
fs._set('/app/src/main.js', 'console.log("Hello from mocked file!");');

console.log('--- Mocking File System ---');
// Simulate reading a file synchronously
try {
  const configContent = fs.readFileSync('/app/data/config.json', 'utf8');
  console.log('Read config.json:', configContent);
  const config = JSON.parse(configContent);
  console.log('Parsed config version:', config.version);
} catch (e) {
  console.error('Error reading config.json:', e.message);
}

// Simulate reading a non-existent file
try {
  fs.readFileSync('/app/data/nonexistent.txt');
} catch (e) {
  console.log('Expected error for non-existent file:', e.message);
}

console.log('\n--- Mocking HTTP Request/Response ---');
// Mock an HTTP server request and response for testing a handler
const mockRequest = new http.ServerRequest({
  url: '/api/items/123',
  method: 'GET',
  headers: { 'Accept': 'application/json', 'User-Agent': 'MockTest' }
});

const mockResponse = new http.ServerResponse();
mockResponse.statusCode = 200;
mockResponse.setHeader('Content-Type', 'application/json');
mockResponse.end(JSON.stringify({ id: '123', name: 'Mock Item' }));

console.log('Mock HTTP Request URL:', mockRequest.url);
console.log('Mock HTTP Request Method:', mockRequest.method);
console.log('Mock HTTP Response Status Code:', mockResponse.statusCode);
console.log('Mock HTTP Response Headers:', mockResponse.getHeaders());
console.log('Mock HTTP Response Body:', mockResponse._getData().toString()); // _getData() retrieves the buffered response