mock-tls-server

Mock up a plain or TLS-encrypted TCP connection without using any actual network facilities or needing any permissions. This is useful for testing, particularly playing around with different TLS failure modes.

WARNING: this package is intended to only be used for testing. It should not be used in any sort of production or Internet-connected setting. In particular, the included Certificate Authority should NEVER be trusted further than individual tests.

Installation

$ npm install --save-dev mock-tls-server

API Documentation

The intent is that the API is similar to that found in Node's net and tls packages. See full docs here.

Example:

import {MockTLSServer, connect} from 'mock-tls-server';

// Expected output: "Welcome!\nexample\n"

const server = new MockTLSServer();
server.listen(4000, sock => {
  sock.write('Welcome!\n');
  sock.pipe(sock);
});

const cli = connect(4000, () => {
  // Send a string, and end the write side of the socket
  // allowHalfOpen is false on both sides by default, so the
  // server will close it's write side in resonse, leading the
  // client to go to the 'closed' state.
  cli.end('example\n');
})
  .on('data', chunk => process.stdout.write(chunk.toString()))
  .on('close', () => server.close());

Always close the server

The server, like a TCP server, will keep the node process from shutting down while it is listening. Make sure to call close() when you are done with it.

If this turns out to be a problem for folks, I'll change it -- please file an issue with ideas.

Use in tests

I use p-event to wait for individual events in async functions:

import pEvent from 'p-event';

await pEvent(client, 'secureConnection');

You can call plainConnect to get a client socket that hasn't been connected with TLS yet, then pass that socket to existing code as a part of its parameters for tls.connect.

import {MockTLSServer, plainConnect} from 'mock-tls-server';
import tls from 'node:tls';

const server = new MockTLSServer({
  notBefore: new Date(new Date().getTime() + 10000), // Invalid because of time
});
server.listen();
await pEvent(server, 'listening');
const socket = plainConnect(server.port);
tls.connect({
  socket,
  host: 'localhost', // Alter this to test name mismatches
  ca: server.ca, // Alter this to test signing failures
});

See the tests in this package for more ideas.

Logging

While you're testing, you'll wonder if anything is actually happening. All of the events that are flowing through the system can be logged by using the NODE_DEBUG environment variable and including mock-tls-server:

NODE_DEBUG=mock-tls-server node examples/echo.js