Why Every DevOps Engineer Should Learn Selenium in 2026

# Start one Chrome browser with WebDriver in a container
# (pin a specific tag in real pipelines instead of latest)
docker run -d --name selenium \
  -p 4444:4444 --shm-size="2g" \
  selenium/standalone-chrome:latest

# Is it ready to accept sessions?
curl -s http://localhost:4444/status | python3 -m json.tool
# look for: "ready": true

# Install the client library for the test
pip install selenium pytest

# tests/test_home.py
import os
from selenium import webdriver
from selenium.webdriver.common.by import By

GRID_URL = os.environ.get("GRID_URL", "http://localhost:4444")
APP_URL = os.environ.get("APP_URL", "https://example.com")

def test_home_page_has_heading():
    options = webdriver.ChromeOptions()
    driver = webdriver.Remote(command_executor=GRID_URL, options=options)
    try:
        driver.get(APP_URL)
        heading = driver.find_element(By.TAG_NAME, "h1")
        assert heading.text.strip() != ""
    finally:
        driver.quit()

# Run: pytest -q tests/

# docker-compose.yml — pin matching tags for hub and nodes
services:
  selenium-hub:
    image: selenium/hub:latest
    ports:
      - "4442:4442"
      - "4443:4443"
      - "4444:4444"

  chrome:
    image: selenium/node-chrome:latest
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443
      - SE_NODE_MAX_SESSIONS=2

  firefox:
    image: selenium/node-firefox:latest
    shm_size: 2gb
    depends_on:
      - selenium-hub
    environment:
      - SE_EVENT_BUS_HOST=selenium-hub
      - SE_EVENT_BUS_PUBLISH_PORT=4442
      - SE_EVENT_BUS_SUBSCRIBE_PORT=4443

# docker compose up -d --scale chrome=3

# Install the official Selenium Grid Helm chart
helm repo add docker-selenium https://www.selenium.dev/docker-selenium
helm repo update

kubectl create namespace selenium
helm install selenium-grid docker-selenium/selenium-grid -n selenium

# Check hub and node pods
kubectl get pods -n selenium

# Reach the Grid from your laptop for a quick check
kubectl port-forward -n selenium svc/selenium-hub 4444:4444
curl -s http://localhost:4444/status

# .github/workflows/ui-tests.yml
name: ui-tests
on: [push]
jobs:
  selenium:
    runs-on: ubuntu-latest
    services:
      selenium:
        image: selenium/standalone-chrome:latest
        ports:
          - 4444:4444
        options: --shm-size=2g
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: "3.12"
      - run: pip install selenium pytest pytest-xdist
      - name: Wait for Selenium
        run: |
          for i in $(seq 1 30); do
            curl -s http://localhost:4444/status | grep -q '"ready": *true' && exit 0
            sleep 2
          done
          exit 1
      - run: pytest -n 2 --junitxml=report.xml tests/
        env:
          GRID_URL: http://localhost:4444
          APP_URL: https://staging.example.com

// Jenkinsfile (declarative, excerpt)
pipeline {
  agent any
  stages {
    stage('Start Grid') {
      steps {
        sh 'docker compose -f selenium-grid.yml up -d --scale chrome=3'
        sh '''
          for i in $(seq 1 30); do
            curl -s http://localhost:4444/status | grep -q '"ready": *true' && exit 0
            sleep 2
          done
          exit 1
        '''
      }
    }
    stage('UI Tests') {
      steps {
        sh 'pytest -n 4 --junitxml=report.xml tests/'
      }
    }
  }
  post {
    always {
      junit 'report.xml'
      sh 'docker compose -f selenium-grid.yml down'
    }
  }
}

#!/usr/bin/env bash
# grid-health.sh — fail fast if the Grid is not usable
GRID=${GRID_URL:-http://localhost:4444}

for i in $(seq 1 30); do
  if curl -s "$GRID/status" | grep -q '"ready": *true'; then
    echo "Grid ready at $GRID"
    exit 0
  fi
  echo "Waiting for Grid... ($i)"
  sleep 2
done

echo "Grid not ready after 60s" >&2
docker compose -f selenium-grid.yml logs --tail=50 || true
exit 1

SELENIUM STAGE FAILURE TRIAGE

Pipeline / build : ____________
Failed tests     : ____ of ____

1. Error type?
   [ ] SessionNotCreated / timeout -> Grid capacity or readiness
   [ ] Chrome crashed / tab crashed -> shared memory (shm_size)
   [ ] NoSuchElement / assertion   -> likely app or test change
   [ ] Connection refused to app   -> environment not deployed
2. Same test failed on last green build? yes / no
3. Passed on retry? yes / no (if yes, mark as flaky, raise ticket)
4. Screenshot / logs attached? yes / no

Verdict: Infra issue / App bug / Test needs fix
Owner  : ____________

# values-ci.yaml — example overrides for the selenium-grid chart
# Check key names against the chart version you install:
#   helm show values docker-selenium/selenium-grid

chromeNode:
  enabled: true
  replicas: 3
  resources:
    requests:
      cpu: "1"
      memory: 2Gi

firefoxNode:
  enabled: false

edgeNode:
  enabled: false

# helm upgrade --install selenium-grid docker-selenium/selenium-grid \
#   -n selenium -f values-ci.yaml