DevOps#selenium-grid #azure-devops #cross-browser-testing #docker #selenium #parallel-testing

How to Integrate Selenium Grid with Azure DevOps

Step-by-step guide to integrating Selenium Grid with Azure DevOps pipelines. Covers Docker-based Selenium Grid setup, self-hosted agents, browser node configuration, running parallel cross-browser tests, and publishing results.

March 20, 2026InnovateBits3 min read

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Selenium Grid lets you run tests across multiple browsers and operating systems in parallel. Integrating it with Azure DevOps gives you scalable, parallel cross-browser test execution in CI without paying for a cloud testing platform.

Selenium Grid architecture in Azure DevOps

Azure Pipeline Agent
       │
       ▼
Docker Compose (on the agent)
  ├── Selenium Hub      (distributes sessions)
  ├── Chrome Node 1     (runs Chrome tests)
  ├── Chrome Node 2     (parallel Chrome)
  └── Firefox Node      (runs Firefox tests)
       │
       ▼
Test code connects to Hub → Hub routes to available Node

Docker Compose for Selenium Grid

# docker-compose.selenium-grid.yml
version: "3"
services:
  selenium-hub:
    image: selenium/hub:4.21.0
    container_name: selenium-hub
    ports:
      - "4444:4444"
    environment:
      - SE_NODE_MAX_SESSIONS=4
 
  chrome-node-1:
    image: selenium/node-chrome:4.21.0
    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
      - SE_VNC_NO_PASSWORD=1
 
  chrome-node-2:
    image: selenium/node-chrome:4.21.0
    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
 
  firefox-node:
    image: selenium/node-firefox:4.21.0
    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

Connecting tests to the Grid

// Java WebDriver connecting to Grid
ChromeOptions options = new ChromeOptions();
options.addArguments("--no-sandbox");
 
WebDriver driver = new RemoteWebDriver(
    new URL("http://localhost:4444/wd/hub"),
    options
);

# Python WebDriver connecting to Grid
from selenium import webdriver
from selenium.webdriver.chrome.options import Options
 
options = Options()
options.add_argument("--no-sandbox")
 
driver = webdriver.Remote(
    command_executor="http://localhost:4444/wd/hub",
    options=options
)

Azure Pipelines YAML

trigger:
  branches:
    include: [main]
 
pool:
  name: Self-Hosted-Linux   # Self-hosted agent with Docker installed
  # Microsoft-hosted agents don't persist Docker between steps — use self-hosted
 
steps:
  - script: |
      docker-compose -f docker-compose.selenium-grid.yml up -d
      echo "Waiting for Grid to be ready..."
      timeout 60 bash -c 'until curl -s http://localhost:4444/wd/hub/status | grep -q "ready.*true"; do sleep 2; done'
    displayName: Start Selenium Grid
 
  - task: JavaToolInstaller@0
    inputs:
      versionSpec: '17'
      jdkArchitectureOption: x64
      jdkSourceOption: PreInstalled
 
  - script: |
      mvn test \
        -DGRID_URL=http://localhost:4444/wd/hub \
        -DBASE_URL=$(STAGING_URL) \
        -Dsurefire.failIfNoSpecifiedTests=false
    displayName: Run cross-browser tests
 
  - task: PublishTestResults@2
    inputs:
      testResultsFormat: JUnit
      testResultsFiles: '**/surefire-reports/TEST-*.xml'
      testRunTitle: Selenium Grid — $(Build.BuildNumber)
      mergeTestResults: true
    condition: always()
 
  - script: docker-compose -f docker-compose.selenium-grid.yml down -v
    displayName: Stop Selenium Grid
    condition: always()

Running tests in parallel across browsers

// TestNG parallel execution across browsers
@DataProvider(name = "browsers", parallel = true)
public Object[][] browsers() {
    return new Object[][] {
        { "chrome" },
        { "firefox" },
    };
}
 
@Test(dataProvider = "browsers")
public void checkoutTest(String browserName) throws MalformedURLException {
    MutableCapabilities caps;
    if ("chrome".equals(browserName)) {
        caps = new ChromeOptions();
    } else {
        caps = new FirefoxOptions();
    }
    
    WebDriver driver = new RemoteWebDriver(
        new URL("http://localhost:4444/wd/hub"), caps
    );
    // Run test...
    driver.quit();
}

Common errors and fixes

Error: Grid hub starts but nodes don't register Fix: Nodes register via the event bus on ports 4442/4443. Ensure these ports are exposed and the SE_EVENT_BUS_HOST env var points to the hub service name (not localhost).

Error: "No such session" errors during parallel execution Fix: Sessions are per-driver instance. Don't share WebDriver instances across threads. Create a new driver per test method.

Error: shm_size has no effect and Chrome crashes Fix: Add --disable-dev-shm-usage to Chrome options. In Docker, /dev/shm is limited to 64MB by default — Chrome needs more for rendering. The option disables shared memory use.

Error: Grid shows nodes as available but tests queue indefinitely Fix: Check SE_NODE_MAX_SESSIONS on each node. If set too low, requests queue. Set to match available CPU cores (2 sessions per CPU core is a good rule).

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