docs: function createStatsCollector(runner) {
    /**
     * @type StatsCollector
     */
    var stats = {
      suites: 0,
      tests: 0,
      passes: 0,
      pending: 0,
      failures: 0
    };
  
    if (!runner) {
      throw new TypeError('Missing runner argument');
    }
  
    runner.stats = stats;
  
    runner.once(EVENT_RUN_BEGIN, function() {
      stats.start = new Date();
    });
    runner.on(EVENT_SUITE_BEGIN, function(suite) {
      suite.root || stats.suites++;
    });
    runner.on(EVENT_TEST_PASS, function() {
      stats.passes++;
    });
    runner.on(EVENT_TEST_FAIL, function() {
      stats.failures++;
    });
    runner.on(EVENT_TEST_PENDING, function() {
      stats.pending++;
    });
    runner.on(EVENT_TEST_END, function() {
      stats.tests++;
    });
    runner.once(EVENT_RUN_END, function() {
      stats.end = new Date();
      stats.duration = stats.end - stats.start;
    });
  }