Performance & Load Testing Patterns Skill

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

| Area | File | Purpose | |------|------|---------| | k6 Load Testing | rules/perf-k6.md | Thresholds, stages, custom metrics, CI integration | | Locust Testing | rules/perf-locust.md | Python load tests, task weighting, auth flows | | Test Types | rules/perf-types.md | Load, stress, spike, soak test patterns | | Execution | rules/execution.md | Coverage reporting, parallel execution, failure analysis | | Pytest Markers | rules/pytest-execution.md | Custom markers, xdist parallel, worker isolation | | Pytest Plugins | rules/pytest-plugins.md | Factory fixtures, plugin hooks, anti-patterns | | k6 Patterns | references/k6-patterns.md | Staged ramp-up, authenticated requests, test types | | xdist Parallel | references/xdist-parallel.md | Distribution modes, worker isolation, CI config | | Custom Plugins | references/custom-plugins.md | conftest plugins, installable plugins, hook reference | | Perf Checklist | checklists/performance-checklist.md | Planning, setup, metrics, load patterns, analysis | | Pytest Checklist | checklists/pytest-production-checklist.md | Config, markers, parallel, fixtures, CI/CD | | Test Template | scripts/test-case-template.md | Full test case documentation template |

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

Performance Test Types

| Type | Duration | VUs | Purpose | When to Use | |------|----------|-----|---------|-------------| | Load | 5-10 min | Expected traffic | Validate normal conditions | Every release | | Stress | 10-20 min | 2-3x expected | Find breaking point | Pre-launch | | Spike | 5 min | Sudden 10x surge | Test auto-scaling | Before events | | Soak | 4-12 hours | Normal load | Detect memory leaks | Weekly/nightly |

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

| Metric | Target | Tool | |--------|--------|------| | p95 response time | < 500ms | k6 | | p99 response time | < 1000ms | k6 | | Error rate | < 1% | k6 / Locust | | Business logic coverage | 90% | pytest-cov | | Critical path coverage | 100% | pytest-cov |

Decision Guide

| Scenario | Recommendation | |----------|----------------| | JavaScript/TypeScript team | k6 for load testing | | Python team | Locust for load testing | | Need CI thresholds | k6 (built-in threshold support) | | Need distributed testing | Locust (built-in distributed mode) | | Slow test suite | pytest-xdist with -n auto | | Flaky parallel tests | --dist loadscope for fixture grouping | | DB-heavy tests | Worker-isolated databases with worker_id |

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

Agent Skills: Performance & Load Testing Patterns

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