add stream backpressure test

test/stream.js

@@ -1,5 +1,6 @@
 const test = require('brittle')
 const b4a = require('b4a')
+const { Readable } = require('streamx')
 const proxy = require('./helpers/proxy')
 const UDX = require('../')
 const { makeTwoStreams } = require('./helpers')
@@ -820,3 +821,46 @@ test('write to unconnected stream', async function (t) {
     socket.close()
   })
 })
+
+test('backpressures stream', async function (t) {
+  t.plan(2)
+
+  const u = new UDX()
+
+  const send = 512 * 1024 * 1024
+
+  let sent = 0
+  let recv = 0
+
+  const socket = u.createSocket()
+  socket.bind(0)
+
+  const a = u.createStream(1)
+  const b = u.createStream(2)
+
+  a.connect(socket, 2, socket.address().port)
+  b.connect(socket, 1, socket.address().port)
+
+  const rs = new Readable({
+    read (cb) {
+      sent += 65536
+      this.push(Buffer.alloc(65536))
+      if (sent === send) this.push(null)
+      cb(null)
+    }
+  })
+
+  rs.pipe(a)
+
+  b.resume()
+  b.on('data', function (data) {
+    recv += data.byteLength
+  })
+  b.on('end', function () {
+    t.is(recv, send)
+    t.ok(send > 0, 'sanity check, sent ' + send + ' bytes')
+
+    b.end()
+    socket.close()
+  })
+})