Testing Perf

Performance & Load Testing Patterns

Focused skill for performance testing, load testing, and pytest execution optimization. Covers k6, Locust, pytest-xdist parallel execution, custom plugins, and test type classification.

Quick Reference

k6 Quick Start

Set up a load test with thresholds and staged ramp-up:

import http from 'k6/http';
import { check, sleep } from 'k6';

export const options = {
  stages: [
    { duration: '30s', target: 20 },  // Ramp up
    { duration: '1m', target: 20 },   // Steady state
    { duration: '30s', target: 0 },   // Ramp down
  ],
  thresholds: {
    http_req_duration: ['p(95)<500'],  // 95th percentile under 500ms
    http_req_failed: ['rate<0.01'],    // Less than 1% error rate
  },
};

export default function () {
  const res = http.get('http://localhost:8000/api/health');
  check(res, {
    'status is 200': (r) => r.status === 200,
    'response time < 200ms': (r) => r.timings.duration < 200,
  });
  sleep(1);
}

Run: k6 run --out json=results.json tests/load/api.js

k6 v1.0+ (May 2025) — what changed

• Native TypeScript: k6 run tests/load/api.ts — no compilation step needed.
• Auto extension provisioning: k6 run pulls required extensions automatically; manual xk6 build is superseded for most workflows.
• Browser module import: import browser from 'k6/browser' — the old k6/experimental/browser path was removed in v0.52+. Any generated code using /experimental/ will fail.
• OTLP output built in: k6 run --out experimental-opentelemetry=... — stream results straight to your tracing backend.

import http from 'k6/http'
import browser from 'k6/browser'
import { check } from 'k6'

export const options = { vus: 5, duration: '30s' }

export default async function () {
  const page = await browser.newPage()
  await page.goto('https://example.com')
  check(page, { 'title present': async p => (await p.title()).length > 0 })
  await page.close()
}

Performance Test Types

pytest Parallel Execution

Speed up test suites with pytest-xdist:

# pyproject.toml
[tool.pytest.ini_options]
addopts = ["-n", "auto", "--dist", "loadscope"]
markers = [
    "slow: marks tests as slow",
    "smoke: critical path tests for CI/CD",
]

# Run with parallel workers and coverage
pytest -n auto --dist loadscope --cov=app --cov-report=term-missing --maxfail=3

# CI fast path — skip slow tests
pytest -m "not slow" -n auto

# Debug mode — single worker
pytest -n 0 -x --tb=long

Worker Database Isolation

When running parallel tests with databases, isolate per worker:

@pytest.fixture(scope="session")
def db_engine(worker_id):
    db_name = f"test_db_{worker_id}" if worker_id != "master" else "test_db"
    engine = create_engine(f"postgresql://localhost/{db_name}")
    yield engine
    engine.dispose()

Key Thresholds

Decision Guide

Related Skills

• ork:testing-unit — Unit testing patterns, pytest fixtures
• ork:testing-e2e — End-to-end performance testing with Playwright
• ork:performance — Core Web Vitals and optimization patterns