fix default option issue

[WLBF]

I get something wrong when I run two autocannon benchmark at same time. However if I run these benchmarks separately it works fine.
example:

const autocannon = require('autocannon');
const util = require('util');

const autocannonFunc = util.promisify(autocannon);

function setupClient {
    ...
}

async function login() {
  try {
    return await autocannonFunc({
      url: 'http://192.168.0.245:10000/login',
      connections: 15,
      pipelining: 1,
      amount: 15,
      bailout: 1,
      method: 'POST',
      setupClient,
    });
  } catch(err) {
      ...
  }
}

async function register() {
  try {
    return await autocannonFunc({
      url: 'http://192.168.0.245:8888/register',
      connections: 1,
      pipelining: 10,
      amount: 20,
      bailout: 1,
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify(body),
    });
  } catch(err) {
      ...
  }
}

Promise.all([login(), register()])

run above code , second autocannon instance will return abnormal 5xx code . I figure out that first calling of run() function change the requests field of defaultOptions object, cause second calling failed. So I think it should be fine to move defaultOptions into function run() block to avoid the side effect.

[mcollina]

I think the proper fix is to switch from xtend to Object.assign in https://github.com/mcollina/autocannon/pull/125/files#diff-de78b50723ff596d7bd35665f36a6cbfR73.

Can you also add a unit test for this?

[WLBF]

sure, I am working on it.

[WLBF]

I think Object.assign only copy first layer of a object. Here we need do full deep copy of defaultOptions object to avoid modification come from run() function. I also adjust the position of defaultOptions to add a unit test.

[mcollina]

Good job! a couple of nits!

[mcollina]

there is no need for this dependency, tap can do it for us.

[mcollina]

you can use t.deepEqual here.

[WLBF]

ok

[mcollina]

LGTM