Reproduces the issue fixed by https://github.com/postwait/node-amqp/pull/293

test-buffer-overwrite.js

require('./harness').run();

var _ = require('lodash');

var NUM_SENDBATCH = 100;
var NUM_DEVNULL = 100;

var enoughIO = false;

connection.addListener('ready', function () {
  puts('connected to ' + connection.serverProperties.product);

  var exchange = connection.exchange('test-buffer-overwrite', {
    'type': 'direct',
    'autoDelete': true
  });

  var qSendBatch = connection.queue('test-buffer-overwrite-sendbatch', {'autoDelete': true}, function() {
    qSendBatch.bind(exchange, 'test-buffer-overwrite-sendbatch');

    var sendBatchRecvCount = 0;
    qSendBatch.subscribe({'ack': true, 'prefetchCount': 15}, function(data, headers, deliveryInfo, message) {
      sendBatchRecvCount++;

      message.acknowledge();

      // Perform a secondary check to ensure that this test
      // is being effectively executed with enough IO
      if (connection.socket.bufferSize > 0) {
        enoughIO = true;
      }

      // Branch out a batch of new messages to generate a bunch of I/O on the
      // _sendMethod path
      _sendDevNullBatch(exchange);

    }).addCallback(function() {
      _triggerNewBatch(exchange);
    });
  });

  var qDevNull = connection.queue('test-buffer-overwrite-devnull', {'autoDelete': true}, function() {
    qDevNull.bind(exchange, 'test-buffer-overwrite-devnull');

    var devNullRecvCount = 0;
    qDevNull.subscribe({'ack': true, 'preferchCount': 15}, function(data, headers, deliveryInfo, message) {
      devNullRecvCount++;

      message.acknowledge();

      // Once we've received each devnull message from each batch, the test has succeeded
      if (devNullRecvCount === NUM_SENDBATCH * NUM_DEVNULL) {
        assert.ok(enoughIO, 'Not enough data was generated from this test to detect an issue');
        setTimeout(connection.end, 1000);
      }
    });
  });
});

var _triggerNewBatch = function(exchange) {
  for (var i = 0; i < NUM_SENDBATCH; i++) {
    exchange.publish('test-buffer-overwrite-sendbatch', {});
  }
};

var _sendDevNullBatch = function(exchange) {
  for (var i = 0; i < NUM_DEVNULL; i++) {
    exchange.publish('test-buffer-overwrite-devnull', _generateMessage());
  }
};

var _generateMessage = function() {
  var result = '';

  // The random size generated here needs to be variable enough to
  // make buffer overwrites matter, and big enough to generate enough
  // I/O to fill up the socket write buffer
  var n = _.random(30000, 31000);
  for (var i = 0; i < n; i++) {
    result += 'a';
  }

  return {'value': result};
};