test: parallel/test-stringbytes-external is too slow

[bnoordhuis]

$ time iojs test/parallel/test-stringbytes-external.js

real   0m3.887s
user   0m3.769s
sys    0m0.157s

It fails sporadically on the rpi1 buildbot: https://jenkins-iojs.nodesource.com/job/node-test-commit-arm/153/nodes=pi1-raspbian-wheezy/tapTestReport/test.tap-667/

/cc @trevnorris

[trevnorris]

Major issue identified. All the string concatenation in the assert.*() calls in the for loops is killing things. e.g. change

// make sure Buffers from externals are the same
for (var i = 0; i < c_bin.length; i++) {
  assert.equal(c_bin[i], c_ucs[i], c_bin[i] + ' == ' + c_ucs[i] +
               ' : index ' + i);
}

to:

// make sure Buffers from externals are the same
for (var i = 0; i < c_bin.length; i++) {
  if (c_bin[i] !== c_ucs[i])
  assert.equal(c_bin[i], c_ucs[i]);
}

a good chunk of time is lost. Same with the other 4 for loops below.

@bnoordhuis Easy fix is to just remove all the string concatenation. Thoughts?

[bnoordhuis]

Seems reasonable to me.

[evanlucas]

Yea, I got it down quite a bit by changing those asserts

[~/dev/code/forks/io.js]
:] ➜ $ time ./iojs test/parallel/test-stringbytes-external.js                                                                                                                     (master) 
        0.36 real         0.33 user         0.03 sys

[trevnorris]

Ref: #2410

[Fishrock123]

Should be fixed in 37ee43e

[rvagg]

going to reopen this, it's failing still/again, e.g. https://ci.nodejs.org/job/node-test-binary-arm/RUN_SUBSET=2,nodes=pi1-raspbian-wheezy/34

not ok 98 test-stringbytes-external.js
  ---
  duration_ms: 208.602
  ...