Selenium Grid

🚀 Selenium Grid: Your Test Army Command Center

Imagine you’re a general with one soldier. You can test one enemy position at a time. But what if you had an ARMY? That’s Selenium Grid!

🎯 The Big Picture

Think of Selenium Grid like a Pizza Delivery HQ:

• You have ONE phone center (the Hub) that takes all orders
• You have MANY delivery drivers (the Nodes) ready to deliver
• Customers can order ANY pizza type (different browsers)
• Multiple deliveries happen at the SAME time (parallel execution)

Result? Tests that took 2 hours now take 10 minutes! 🎉

🏗️ Grid Architecture

What Is It?

Selenium Grid is a smart server that lets you run tests on MANY computers at once.

graph TD
    A["Your Test Code"] --> B["Hub - The Boss"]
    B --> C["Node 1 - Chrome"]
    B --> D["Node 2 - Firefox"]
    B --> E["Node 3 - Safari"]

The Two Heroes

Simple Example

// Your test talks to the Hub
// Hub finds the right Node
// Node runs your test
// Results come back to you!

Why This Rocks:

• ✅ One place to manage everything
• ✅ Tests run on many machines
• ✅ No need to install browsers everywhere

🔧 Hub and Node Setup

Step 1: Start the Hub

The Hub is your command center. Start it first!

java -jar selenium-server.jar hub

That’s it! Hub runs on http://localhost:4444

Step 2: Start Nodes

Nodes are your workers. They do the actual testing.

java -jar selenium-server.jar node

The Node automatically finds and joins the Hub!

Visual: How They Connect

graph TD
    H["Hub :4444"] --> N1["Node 1"]
    H --> N2["Node 2"]
    H --> N3["Node 3"]
    N1 --> B1["Chrome"]
    N2 --> B2["Firefox"]
    N3 --> B3["Edge"]

Pro Setup Example

# Start Hub on specific port
java -jar selenium-server.jar hub \
  --port 4444

# Start Node connecting to Hub
java -jar selenium-server.jar node \
  --hub http://hub-ip:4444

Remember:

• 🟢 Start Hub FIRST
• 🟢 Then start Nodes
• 🟢 Nodes find Hub automatically

🌐 Remote WebDriver Connection

The Magic Bridge

Instead of talking to a local browser, your code talks to the Grid!

Before (Local):

WebDriver driver = new ChromeDriver();
// Runs on YOUR machine only

After (Remote):

URL hubUrl = new URL(
  "http://localhost:4444/wd/hub"
);

ChromeOptions options =
  new ChromeOptions();

WebDriver driver = new RemoteWebDriver(
  hubUrl,
  options
);
// Runs on ANY available Node!

What Changed?

Key Parts

1. Hub URL - Where to send requests
2. Capabilities - What browser you want
3. RemoteWebDriver - The connection magic

// Full example
DesiredCapabilities caps =
  new DesiredCapabilities();
caps.setBrowserName("firefox");

RemoteWebDriver driver =
  new RemoteWebDriver(
    new URL("http://grid:4444/wd/hub"),
    caps
  );

🎯 Distributed Test Execution

What Does “Distributed” Mean?

Your tests run on different machines at the same time!

graph LR
    T["Test Suite"] --> H["Hub"]
    H --> M1["Machine 1"]
    H --> M2["Machine 2"]
    H --> M3["Machine 3"]

Why It’s Amazing

Without Grid:

• 100 tests × 1 minute each = 100 minutes ⏰

With Grid (10 Nodes):

• 100 tests ÷ 10 nodes = 10 minutes! 🚀

Real Example

// Test 1 goes to Node A
// Test 2 goes to Node B
// Test 3 goes to Node C
// All run at the SAME time!

Setting Up Distribution

Your test framework handles this. Example with TestNG:

<suite name="Distributed"
       parallel="tests"
       thread-count="5">
  <test name="Test1">
    <!-- runs on available node -->
  </test>
  <test name="Test2">
    <!-- runs on another node -->
  </test>
</suite>

Key Benefit: Hub automatically sends tests to available Nodes!

🌈 Cross-Browser Testing

The Problem

Your website must work on:

• Chrome 🟢
• Firefox 🟠
• Safari 🔵
• Edge 🔷

Testing one by one? Painful!

The Solution

Grid runs ALL browsers at once!

graph TD
    T["Your Test"] --> H["Hub"]
    H --> C["Chrome Node"]
    H --> F["Firefox Node"]
    H --> S["Safari Node"]
    H --> E["Edge Node"]

Code Example

// For Chrome
ChromeOptions chrome =
  new ChromeOptions();
WebDriver chromeDriver =
  new RemoteWebDriver(hubUrl, chrome);

// For Firefox
FirefoxOptions firefox =
  new FirefoxOptions();
WebDriver firefoxDriver =
  new RemoteWebDriver(hubUrl, firefox);

The Magic: Capabilities

Tell Grid what you need:

DesiredCapabilities caps =
  new DesiredCapabilities();

// I want Firefox!
caps.setBrowserName("firefox");

// On Windows!
caps.setPlatform(Platform.WINDOWS);

// Hub finds matching Node

Browser Coverage Table

⚡ Parallel Test Execution

The Speed Secret

Parallel = Running tests side by side, not one after another.

Visual Comparison

Sequential (Slow):

Test1 ████████
              Test2 ████████
                            Test3 ████████
Total: 24 seconds

Parallel (Fast):

Test1 ████████
Test2 ████████
Test3 ████████
Total: 8 seconds!

How to Enable Parallel

TestNG Example:

<suite parallel="methods"
       thread-count="10">
  <test name="ParallelTest">
    <classes>
      <class name="MyTests"/>
    </classes>
  </test>
</suite>

JUnit 5 Example:

# junit-platform.properties
junit.jupiter.execution
  .parallel.enabled=true
junit.jupiter.execution
  .parallel.mode.default=concurrent

Best Practices

1. Independent Tests - Tests shouldn’t share data
2. Thread-Safe Code - No shared variables
3. Unique Test Data - Each test uses own data

// GOOD - Each test has own driver
@Test
void testLogin() {
  WebDriver driver = createDriver();
  // test code
  driver.quit();
}

// BAD - Shared driver causes problems
static WebDriver sharedDriver; // Don't!

Scaling Formula

🎮 Putting It All Together

Complete Setup Flow

graph TD
    A["1. Download Selenium Server"] --> B["2. Start Hub"]
    B --> C["3. Start Nodes"]
    C --> D["4. Write Remote Tests"]
    D --> E["5. Run in Parallel"]
    E --> F["6. Get Fast Results!"]

Quick Start Commands

# Terminal 1: Start Hub
java -jar selenium-server.jar hub

# Terminal 2: Start Chrome Node
java -jar selenium-server.jar node \
  --detect-drivers true

# Terminal 3: Run your tests!
mvn test

Complete Test Example

public class GridTest {
  WebDriver driver;

  @BeforeEach
  void setup() throws Exception {
    URL hub = new URL(
      "http://localhost:4444/wd/hub"
    );

    ChromeOptions options =
      new ChromeOptions();

    driver = new RemoteWebDriver(
      hub, options
    );
  }

  @Test
  void testGoogle() {
    driver.get("https://google.com");
    // Your test here
  }

  @AfterEach
  void teardown() {
    if (driver != null) {
      driver.quit();
    }
  }
}

🏆 Key Takeaways

🚀 Your Next Steps

1. ✅ Download Selenium Server JAR
2. ✅ Start a Hub locally
3. ✅ Connect one Node
4. ✅ Convert one test to RemoteWebDriver
5. ✅ Watch the magic happen!

“One test at a time is like having one checkout lane at a supermarket. Selenium Grid opens ALL the lanes!” 🛒

You’ve got this! 💪