Error Rate Metric Bug

// Summarizes results from a load test run
function calculateMetrics(responses) {
  let totalTime = 0;
  let errors = 0;
  for (const r of responses) {
    totalTime += r.responseTime;
    if (r.status >= 400) errors++;
  }
  const avgResponseTime = totalTime / responses.length;
  const errorRate = (errors / (responses.length - errors)) * 100;
  return { avgResponseTime, errorRate };
}