test.js

import path from 'path'
import { fileURLToPath } from 'url'
import { execa } from 'execa'
import pDefer from 'p-defer'
import { toString as uint8ArrayToString } from 'uint8arrays/to-string'

const __dirname = path.dirname(fileURLToPath(import.meta.url))

function startProcess (name) {
  return execa('node', [path.join(__dirname, name)], {
    cwd: path.resolve(__dirname),
    all: true
  })
}

const listenerReady = pDefer()
const messageReceived = pDefer()

// Step 1 process
process.stdout.write('node src/listener.js\n')
const listenerProc = startProcess('src/listener.js')
listenerProc.all.on('data', async (data) => {
  process.stdout.write(data)
  const s = uint8ArrayToString(data)

  if (s.includes('Listener ready, listening on:')) {
    listenerReady.resolve()
  }
})

await listenerReady.promise
process.stdout.write('==================================================================\n')

// Step 2 process
process.stdout.write('node src/dialer.js\n')
const dialerProc = startProcess('src/dialer.js')
dialerProc.all.on('data', async (data) => {
  process.stdout.write(data)
  const s = uint8ArrayToString(data)

  if (s.includes('received echo:')) {
    messageReceived.resolve()
  }
})

await messageReceived.promise
process.stdout.write('echo message received\n')

listenerProc.kill()
dialerProc.kill()
await Promise.all([
  listenerProc,
  dialerProc
]).catch((err) => {
  if (err.signal !== 'SIGTERM') {
    throw err
  }
})