node/test/parallel/test-buffer-concat.js

'use strict';
require('../common');
var assert = require('assert');

var zero = [];
var one  = [ Buffer.from('asdf') ];
var long = [];
for (var i = 0; i < 10; i++) long.push(Buffer.from('asdf'));

var flatZero = Buffer.concat(zero);
var flatOne = Buffer.concat(one);
var flatLong = Buffer.concat(long);
var flatLongLen = Buffer.concat(long, 40);

assert(flatZero.length === 0);
assert(flatOne.toString() === 'asdf');
// A special case where concat used to return the first item,
// if the length is one. This check is to make sure that we don't do that.
assert(flatOne !== one[0]);
assert(flatLong.toString() === (new Array(10 + 1).join('asdf')));
assert(flatLongLen.toString() === (new Array(10 + 1).join('asdf')));

assertWrongList();
assertWrongList(null);
assertWrongList(Buffer.from('hello'));
assertWrongList([42]);
assertWrongList(['hello', 'world']);
assertWrongList(['hello', Buffer.from('world')]);

function assertWrongList(value) {
  assert.throws(function() {
    Buffer.concat(value);
  }, function(err) {
    return err instanceof TypeError &&
           err.message === '"list" argument must be an Array of Buffers';
  });
}