Add k6-load-testing skill for API and performance testing (#287)
* I've created a new skill called k6-load-testing * add k6-load-testing skill for API and performance testing * add k6-load-testing skill for API and performance testing * fixed errors related to the skill * minor fix
This commit is contained in:
Kairo Official
GitHub
627
skills/k6-load-testing/SKILL.md
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627
skills/k6-load-testing/SKILL.md
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---
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name: k6-load-testing
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description: "Comprehensive k6 load testing skill for API, browser, and scalability testing. Write realistic load scenarios, analyze results, and integrate with CI/CD."
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category: testing
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risk: safe
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source: community
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date_added: "2026-03-13"
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author: Kairo Official
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tags: [k6, load-testing, performance, api-testing, ci-cd]
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tools: [claude, cursor, gemini]
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---
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# k6 Load Testing
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## Overview
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k6 is a modern, developer-centric load testing tool that helps you write and execute performance tests for HTTP APIs, WebSocket endpoints, and browser scenarios. This skill provides comprehensive guidance on writing realistic load tests, configuring test scenarios (smoke, load, stress, spike, soak), analyzing results, and integrating with CI/CD pipelines.
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Use this skill when you need to validate system performance, identify bottlenecks, ensure SLA compliance, or catch performance regressions before deployment.
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---
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## When to Use This Skill
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- Use when you need to load test HTTP APIs, WebSocket endpoints, or browser scenarios
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- Use when setting up performance regression tests in CI/CD
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- Use when analyzing system behavior under various load conditions
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- Use when comparing performance between code changes
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- Use when validating SLA requirements and performance budgets
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---
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## k6 Basics
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### Installation
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```bash
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# macOS
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brew install k6
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# Windows
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choco install k6
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# Linux
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sudo gpg -k
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sudo gpg --no-default-keyring --keyring /usr/share/keyrings/k6-archive-keyring.gpg --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys C5AD17C747E3415A3642D57D77C6C491D6AC1D69
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echo "deb [signed-by=/usr/share/keyrings/k6-archive-keyring.gpg] https://dl.k6.io/deb stable main" | sudo tee /etc/apt/sources.list.d/k6.list
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sudo apt-get update
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sudo apt-get install k6
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```
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### Quick Start
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```javascript
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// simple-test.js
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import http from 'k6/http';
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import { check, sleep } from 'k6';
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export const options = {
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vus: 10,
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duration: '30s',
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};
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export default function () {
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const res = http.get('https://httpbin.test.k6.io/get');
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check(res, {
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'status is 200': (r) => r.status === 200,
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'response time < 500ms': (r) => r.timings.duration < 500,
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});
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sleep(1);
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}
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```
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Run with: `k6 run simple-test.js`
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---
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## Test Configuration
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### Common Options
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```javascript
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export const options = {
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// Virtual Users (concurrent users)
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vus: 100,
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// Test duration
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duration: '5m',
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// Or use stages for ramp-up/ramp-down
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stages: [
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{ duration: '30s', target: 20 }, // Ramp up
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{ duration: '1m', target: 100 }, // Stay at 100
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{ duration: '30s', target: 0 }, // Ramp down
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],
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// Thresholds (SLA)
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thresholds: {
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http_req_duration: ['p(95)<500'], // 95% requests < 500ms
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http_req_failed: ['rate<0.01'], // Error rate < 1%
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},
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// Load zones (distributed testing)
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ext: {
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loadimpact: {
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name: 'My Load Test',
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distribution: {
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'amazon:us:ashburn': { weight: 50 },
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'amazon:eu: Dublin': { weight: 50 },
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},
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},
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},
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};
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```
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### Test Types
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| Type | Use Case | Configuration |
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|------|----------|---------------|
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| Smoke Test | Verify basic functionality | Low VUs (1-5), short duration |
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| Load Test | Normal expected load | Target VUs based on traffic |
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| Stress Test | Find breaking point | Ramp beyond capacity |
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| Spike Test | Sudden traffic spikes | Rapid increase/decrease |
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| Soak Test | Long-term stability | Extended duration |
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---
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## HTTP Testing
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### Basic Requests
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```javascript
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import http from 'k6/http';
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import { check, sleep } from 'k6';
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export default function () {
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// GET request
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const getRes = http.get('https://api.example.com/users');
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check(getRes, {
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'GET succeeded': (r) => r.status === 200,
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'has users': (r) => r.json('data.length') > 0,
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});
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// POST request with JSON body
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const postRes = http.post('https://api.example.com/users',
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JSON.stringify({ name: 'Test User', email: 'test@example.com' }),
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{
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headers: {
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'Content-Type': 'application/json',
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'Authorization': 'Bearer ' + __ENV.API_TOKEN,
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},
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}
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);
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check(postRes, {
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'POST succeeded': (r) => r.status === 201,
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'user created': (r) => r.json('id') !== undefined,
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});
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sleep(1);
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}
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```
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### Request Chaining
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```javascript
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import http from 'k6/http';
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import { check } from 'k6';
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export default function () {
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// Login and extract token
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const loginRes = http.post('https://api.example.com/login',
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JSON.stringify({ email: 'test@example.com', password: 'password123' })
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);
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const token = loginRes.json('access_token');
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// Use token in subsequent requests
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const headers = {
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'Authorization': `Bearer ${token}`,
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'Content-Type': 'application/json',
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};
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const profileRes = http.get('https://api.example.com/profile', {
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headers: headers,
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});
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check(profileRes, {
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'profile loaded': (r) => r.status === 200,
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});
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}
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```
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### Parameterized Testing
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```javascript
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import http from 'k6/http';
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import { check } from 'k6';
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const usernames = ['user1', 'user2', 'user3', 'user4', 'user5'];
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export default function () {
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// Use shared array with VU-specific index
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const username = usernames[__VU % usernames.length];
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const res = http.get(`https://api.example.com/users/${username}`);
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check(res, {
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'user found': (r) => r.status === 200,
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});
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}
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```
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---
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## Browser Testing (k6 Browser)
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```javascript
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import { browser } from 'k6/browser';
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export const options = {
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scenarios: {
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browser_test: {
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executor: 'constant-vus',
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vus: 5,
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duration: '30s',
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browser: {
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type: 'chromium',
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},
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},
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},
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};
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export default async function () {
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const page = await browser.newPage();
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try {
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await page.goto('https://example.com');
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const title = await page.title();
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console.log(`Page title: ${title}`);
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// Click and interact
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await page.click('button[data-testid="submit"]');
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// Wait for response
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await page.waitForSelector('.success-message');
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} finally {
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await page.close();
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}
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}
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```
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Install browser support: `k6 install chromium`
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---
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## WebSocket Testing
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```javascript
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import ws from 'k6/ws';
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import { check } from 'k6';
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export default function () {
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const url = 'wss://echo.websocket.org';
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ws.connect(url, {}, function (socket) {
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socket.on('open', () => {
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console.log('WebSocket connected');
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socket.send('Hello WebSocket');
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});
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socket.on('message', (data) => {
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console.log(`Received: ${data}`);
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check(data, {
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'echo received': (d) => d.includes('Hello'),
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});
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});
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socket.on('close', () => {
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console.log('WebSocket closed');
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});
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// Send periodic messages
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socket.setInterval(function () {
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socket.send('ping');
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}, 1000);
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// Close after 5 seconds
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socket.setTimeout(function () {
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socket.close();
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}, 5000);
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});
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}
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```
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---
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## Data Handling
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### CSV Data Source
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```javascript
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import http from 'k6/http';
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import { check } from 'k6';
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import { SharedArray } from 'k6/data';
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// Option 1: Load once, shared across VUs
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const users = new SharedArray('users', function () {
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return open('./users.csv').split('\n').slice(1).map(line => {
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const [email, password] = line.split(',');
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return { email, password };
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});
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});
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export default function () {
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const user = users[__VU % users.length];
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const res = http.post('https://api.example.com/login',
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JSON.stringify({ email: user.email, password: user.password })
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);
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check(res, { 'login successful': (r) => r.status === 200 });
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}
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```
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### JSON Data Source
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```javascript
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import http from 'k6/http';
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import { check } from 'k6';
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import { SharedArray } from 'k6/data';
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const products = new SharedArray('products', function () {
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return JSON.parse(open('./products.json'));
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});
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export default function () {
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const product = products[Math.floor(Math.random() * products.length)];
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const res = http.get(`https://api.example.com/products/${product.id}`);
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check(res, { 'product found': (r) => r.status === 200 });
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}
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```
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---
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## Thresholds & SLA
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### Basic Thresholds
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```javascript
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export const options = {
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vus: 50,
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duration: '2m',
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thresholds: {
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// Response time thresholds
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http_req_duration: ['p(95)<500', 'p(99)<1000'],
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// Error rate threshold
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http_req_failed: ['rate<0.01'],
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// Throughput threshold
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http_reqs: ['rate>100'],
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},
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};
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```
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### Advanced Thresholds
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```javascript
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export const options = {
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thresholds: {
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// Multiple thresholds on same metric
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http_req_duration: [
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'p(90)<300', // 90th percentile < 300ms
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'p(95)<500', // 95th percentile < 500ms
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'p(99)<1000', // 99th percentile < 1s
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'avg<200', // average < 200ms
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],
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// Custom metrics
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my_custom_metric: ['avg<100'],
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// Abort on threshold failure
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'http_req_duration{method:GET}': ['p(95)<300'],
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},
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};
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```
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---
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## Custom Metrics
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### Counters
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```javascript
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import http from 'k6/http';
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import { Counter, Trend, Rate, Gauge } from 'k6/metrics';
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// Define custom metrics
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const myCounter = new Counter('api_calls_total');
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const responseTime = new Trend('response_time');
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const errorRate = new Rate('error_rate');
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const activeUsers = new Gauge('active_users');
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export default function () {
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const res = http.get('https://api.example.com/data');
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// Increment counter
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myCounter.add(1);
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// Add to trend (for percentiles)
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responseTime.add(res.timings.duration);
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// Track error rate
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errorRate.add(res.status !== 200);
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// Set gauge value
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activeUsers.add(__VU);
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// Tagged metrics
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const taggedRes = http.get('https://api.example.com/users', {
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tags: { endpoint: 'users', env: 'prod' },
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});
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}
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```
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---
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## CI/CD Integration
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### GitHub Actions
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```yaml
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# .github/workflows/load-test.yml
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name: Load Tests
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on:
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push:
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branches: [main]
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schedule:
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- cron: '0 2 * * *' # Daily at 2 AM
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jobs:
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load-test:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v4
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- name: Setup k6
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uses: grafana/k6-action@v0.2.0
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- name: Run load test
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env:
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API_TOKEN: ${{ secrets.API_TOKEN }}
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run: k6 run --out json=results.json load-test.js
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- name: Upload results
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uses: actions/upload-artifact@v4
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with:
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name: k6-results
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path: results.json
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- name: Check thresholds
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if: failure()
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run: |
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echo "Load test failed thresholds!"
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exit 1
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```
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### GitLab CI
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```yaml
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# .gitlab-ci.yml
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load_test:
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image: grafana/k6:latest
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script:
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- k6 run load-test.js
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artifacts:
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when: always
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paths:
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- results.json
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reports:
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junit: results.xml
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```
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---
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## Results Analysis
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### Built-in Reports
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```bash
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# Text summary
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k6 run load-test.js
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# JSON output for parsing
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k6 run --out json=results.json load-test.js
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# InfluxDB + Grafana
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k6 run --out influxdb=http://localhost:8086/k6 load-test.js
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# Prometheus remote write
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k6 run --out prometheus=localhost:9090/k6 load-test.js
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# Cloud results
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k6 run --out cloud load-test.js
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```
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### Interpreting Results
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| Metric | Description | Good | Warning | Bad |
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|--------|-------------|------|---------|-----|
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| http_req_duration (p95) | 95% response time | < 300ms | 300-500ms | > 500ms |
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| http_req_failed | Error rate | < 0.1% | 0.1-1% | > 1% |
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| http_reqs | Requests/sec | Meeting target | Near limit | At limit |
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| vus | Virtual users | Stable | Gradual increase | Unexpected spike |
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---
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## Examples
|
||||
|
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### Example 1: Basic API Load Test
|
||||
|
||||
```javascript
|
||||
import http from 'k6/http';
|
||||
import { check, sleep } from 'k6';
|
||||
|
||||
export const options = {
|
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vus: 50,
|
||||
duration: '2m',
|
||||
thresholds: {
|
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http_req_duration: ['p(95)<500'],
|
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http_req_failed: ['rate<0.01'],
|
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},
|
||||
};
|
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|
||||
export default function () {
|
||||
const res = http.get('https://api.example.com/users');
|
||||
|
||||
check(res, {
|
||||
'status is 200': (r) => r.status === 200,
|
||||
'response time < 500ms': (r) => r.timings.duration < 500,
|
||||
});
|
||||
|
||||
sleep(1);
|
||||
}
|
||||
```
|
||||
|
||||
### Example 2: Test with Authentication and Data Parameterization
|
||||
|
||||
```javascript
|
||||
import http from 'k6/http';
|
||||
import { check } from 'k6';
|
||||
import { SharedArray } from 'k6/data';
|
||||
|
||||
const users = new SharedArray('users', function () {
|
||||
return JSON.parse(open('./users.json'));
|
||||
});
|
||||
|
||||
export default function () {
|
||||
const user = users[__VU % users.length];
|
||||
|
||||
const loginRes = http.post('https://api.example.com/login',
|
||||
JSON.stringify({ email: user.email, password: user.password })
|
||||
);
|
||||
|
||||
const token = loginRes.json('access_token');
|
||||
|
||||
const headers = { 'Authorization': `Bearer ${token}` };
|
||||
const res = http.get('https://api.example.com/profile', { headers });
|
||||
|
||||
check(res, { 'profile loaded': (r) => r.status === 200 });
|
||||
}
|
||||
```
|
||||
|
||||
---
|
||||
|
||||
## Best Practices
|
||||
|
||||
- **Start with smoke test**: Verify test works with 1-5 VUs before scaling up
|
||||
- **Use realistic data**: Parameterize with real user data and behaviors
|
||||
- **Set meaningful thresholds**: Match your SLA and business requirements
|
||||
- **Warm up systems**: Include ramp-up time in stages
|
||||
- **Monitor external dependencies**: Track not just your APIs but downstream services
|
||||
- **Use tags**: Tag requests for granular analysis (`tags: { endpoint: 'users' }`)
|
||||
- **Keep tests focused**: One test file per scenario for clarity
|
||||
|
||||
---
|
||||
|
||||
## Common Pitfalls
|
||||
|
||||
- **Problem:** Tests pass locally but fail in CI
|
||||
**Solution:** Ensure CI environment has similar resources and network conditions
|
||||
|
||||
- **Problem:** Inconsistent results between runs
|
||||
**Solution:** Check for external dependencies, random data, or test data pollution
|
||||
|
||||
- **Problem:** k6 runs out of memory
|
||||
**Solution:** Use ` SharedArray` for large data, reduce VUs, or use `--max-memory` flag
|
||||
|
||||
- **Problem:** Thresholds too strict
|
||||
**Solution:** Start with relaxed thresholds, tighten based on historical data
|
||||
|
||||
---
|
||||
|
||||
## Related Skills
|
||||
|
||||
- `@performance-engineer` - For broader performance optimization
|
||||
- `@api-testing-observability-api-mock` - For API mocking during testing
|
||||
- `@application-performance-performance-optimization` - For performance optimization
|
||||
|
||||
---
|
||||
|
||||
## Additional Resources
|
||||
|
||||
- [k6 Documentation](https://k6.io/docs/)
|
||||
- [k6 Examples](https://github.com/grafana/k6/tree/master/examples)
|
||||
- [k6 Load Testing Guides](https://k6.io/guides/)
|
||||
- [k6 Cloud](https://k6.io/cloud/)
|
||||
Reference in New Issue
Block a user