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