Adding batches asynchronously to a Vows suite

Question

I've got some code like this. The idea is that I'm reading fixture data from files and using the data from each file to add a batch:

// test.js
var vows = require('vows')
  , async = require('async')
  , suite;

exports.suite = suite = vows.describe('My tests');

function run_tests() {
  set_up = [
    find_tests(tests_path)  // gets test data
  ];

  async.series(set_up, function(errs, tests) {
    tests = tests.pop();
    tests.forEach(function(test) {
      var batch = make_batch(test);  // makes a batch 
      suite.addBatch(batch);
    })
  });

}

run_tests();

Obviously vows test.js doesn't find any tests because the batches are added asynchronously. I've got no idea how to make this work though. I want to use vows to be able to use reporters.