Adding MockPortBinding.writeToPort & MockBinding.getOpenMockPort()

[Lucas-C]

Usage example
Adding those methods allows to define a synchronous function that creates a pair of communicating virtual ports:

import { MockBinding } from '@serialport/binding-mock'
import { SerialPortStream } from "@serialport/stream";

const virtualPortsPair = ({ portName1 = "/dev/ttyCOM1", portName2 = "/dev/ttyCOM2", autoOpen = true }: {portName1?: string; portName2?: string; autoOpen?: boolean } = {}): SerialPortStream[] => {
  MockBinding.createPort(portName1, { echo: false, record: false });
  MockBinding.createPort(portName2, { echo: false, record: false });

  const com1 = new SerialPortStream({ binding: MockBinding, path: portName1, baudRate: 9600, autoOpen });
  const com2 = new SerialPortStream({ binding: MockBinding, path: portName2, baudRate: 9600, autoOpen });

  com1.on("open", () => {
    com2.on("open", () => {
      const mockPort1 = MockBinding.getOpenMockPort(portName1);
      const mockPort2 = MockBinding.getOpenMockPort(portName2);
      mockPort1.writeToPort = mockPort2;
      mockPort2.writeToPort = mockPort1;
    });
  });

  return [com1, com2];
};

This is a very useful pattern for unit test suites of end applications.

[reconbot]

I think this is a great idea, anything to make it easier.

I'd like to suggest you see about adding it to the ports object which is roughly an analog to the hardware, vs adding it to the open port objects which is the software listening to the hardware.

There can actually be multiple software ports reading one hardware port. (I have no idea how the mocks handle that) but at the very least being able to hook together hardware ports without them being open first would be easier.