Docker Selenium Grid in Selenium Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a Selenium Grid hub container using Docker.

Selenium Java

docker run -d -p 4444:4444 --name selenium-hub [1]

Drag options to blanks, or click blank then click option'

Aselenium/standalone-chrome:4.8.0

Bselenium/hub:4.8.0

Cselenium/node-firefox:4.8.0

Dselenium/node-chrome:4.8.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using a node image instead of the hub image.

Not exposing port 4444.

The Selenium Grid hub runs the central server. The correct Docker image is selenium/hub:4.8.0.

2fill in blank

medium

Complete the code to start a Chrome node container and connect it to the Selenium Grid hub network.

Selenium Java

docker run -d --network [1] --name chrome-node -e SE_EVENT_BUS_HOST=selenium-hub selenium/node-chrome:4.8.0

Drag options to blanks, or click blank then click option'

Abridge

Bhost

Cselenium-grid

Ddefault

Attempts:

3 left

💡 Hint

Common Mistakes

Using the default or host network which isolates containers.

Not specifying the network, causing communication failure.

The Chrome node must join the same Docker network as the Selenium Grid hub, commonly named selenium-grid.

3fill in blank

hard

Fix the error in the Docker command to start a Firefox node connected to the Selenium Grid hub.

Selenium Java

docker run -d --network selenium-grid --name firefox-node -e SE_EVENT_BUS_HOST=[1] selenium/node-firefox:4.8.0

Drag options to blanks, or click blank then click option'

Aselenium-hub

B127.0.0.1

Cfirefox-node

Dlocalhost

Attempts:

3 left

💡 Hint

Common Mistakes

Using localhost or 127.0.0.1 which refers to the node container itself.

Using the node's own name instead of the hub's name.

The environment variable SE_EVENT_BUS_HOST must be set to the hub container's name selenium-hub so the node can connect correctly.

4fill in blank

hard

Fill both blanks to create a Docker network and start the Selenium Grid hub attached to it.

Selenium Java

docker network [1] selenium-grid

docker run -d -p 4444:4444 --network [2] --name selenium-hub selenium/hub:4.8.0

Drag options to blanks, or click blank then click option'

Acreate

Bremove

Cselenium-grid

Dbridge

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'remove' instead of 'create' for the network command.

Not matching the network name in both commands.

First, create the Docker network named selenium-grid with docker network create selenium-grid. Then start the hub attached to this network.

5fill in blank

hard

Fill all three blanks to write a Java Selenium test that connects to the Selenium Grid hub and opens a Chrome browser.

Selenium Java

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.remote.RemoteWebDriver;
import java.net.URL;

public class GridTest {
    public static void main(String[] args) throws Exception {
        ChromeOptions options = new ChromeOptions();
        WebDriver driver = new RemoteWebDriver(new URL("[1]"), [2]);
        driver.get("https://example.com");
        System.out.println(driver.getTitle());
        driver.quit();
    }
}

Drag options to blanks, or click blank then click option'

Ahttp://localhost:4444/wd/hub

Boptions

Cnew ChromeOptions()

Dhttp://selenium-hub:4444/wd/hub

Attempts:

3 left

💡 Hint

Common Mistakes

Using localhost in the URL which won't work inside Docker network.

Passing a new ChromeOptions() instead of the existing options variable.

The Selenium Grid hub URL inside Docker network is http://selenium-hub:4444/wd/hub. The second argument to RemoteWebDriver is the ChromeOptions object named options.

Practice

1. What is the main purpose of using Docker Selenium Grid in automated testing?

easy

A. To debug Java code in Selenium tests

B. To write test scripts faster

C. To replace Selenium WebDriver completely

D. To run tests on multiple browsers and machines simultaneously

Solution

1. Step 1: Understand Docker Selenium Grid's role

   Docker Selenium Grid allows running tests on different browsers and machines at the same time, improving test coverage and speed.

2. Step 2: Compare options with this purpose

   Only To run tests on multiple browsers and machines simultaneously matches this main purpose. Options B, C, and D describe unrelated or incorrect uses.

3. Final Answer:

   To run tests on multiple browsers and machines simultaneously -> Option D

4. Quick Check:

   Purpose = run tests on many browsers [OK]

Hint: Docker Selenium Grid = run tests on many browsers [OK]

Common Mistakes:

• Thinking it speeds up writing tests
• Confusing it with Selenium WebDriver itself
• Assuming it is for debugging code

2. Which Docker command correctly starts a Selenium Grid Hub container?

easy

A. docker start selenium/node-chrome

B. docker build -t selenium/hub .

C. docker run -d -p 4444:4444 selenium/hub

D. docker stop selenium/hub

Solution

1. Step 1: Identify the command to run a container

   The command to start a container in detached mode and map port 4444 is 'docker run -d -p 4444:4444 selenium/hub'.

2. Step 2: Check other options

   docker start selenium/node-chrome starts an existing container, C builds an image, and D stops a container. Only B starts the hub container correctly.

3. Final Answer:

   docker run -d -p 4444:4444 selenium/hub -> Option C

4. Quick Check:

   Start hub = docker run -d -p 4444:4444 selenium/hub [OK]

Hint: Use 'docker run -d -p 4444:4444 selenium/hub' to start hub [OK]

Common Mistakes:

• Using 'docker start' instead of 'docker run' to create container
• Confusing build and run commands
• Stopping instead of starting the container

3. Given this Java code snippet connecting to a Docker Selenium Grid hub:

RemoteWebDriver driver = new RemoteWebDriver(
  new URL("http://localhost:4444/wd/hub"),
  new ChromeOptions()
);
driver.get("https://example.com");
System.out.println(driver.getTitle());

What will be printed if the page title is "Example Domain"?

medium

A. Example Domain

B. http://localhost:4444/wd/hub

C. null

D. NoSuchSessionException

Solution

1. Step 1: Understand RemoteWebDriver usage

   The code creates a RemoteWebDriver connected to the Selenium Grid hub URL and opens the page https://example.com.

2. Step 2: Check what driver.getTitle() returns

   driver.getTitle() returns the page title, which is "Example Domain" for that URL.

3. Final Answer:

   Example Domain -> Option A

4. Quick Check:

   driver.getTitle() = page title [OK]

Hint: driver.getTitle() prints page title loaded [OK]

Common Mistakes:

• Confusing URL with page title
• Expecting null if no errors
• Assuming exceptions without errors

4. You run this command to start a Chrome node:

docker run -d --link selenium-hub:hub selenium/node-chrome

But your tests fail to connect to the node. What is the likely problem?

medium

A. The Docker daemon is stopped

B. The node container is not linked properly to the hub

C. The Chrome browser is not installed inside the node container

D. The hub container is not running

Solution

1. Step 1: Analyze the linking option

   The '--link' option is deprecated and may not correctly link the node to the hub, causing connection failure.

2. Step 2: Check other possible causes

   Docker daemon (A) or hub not running (B) issues would cause broader failures. Chrome is preinstalled in official node images (C) so unlikely cause.

3. Final Answer:

   The node container is not linked properly to the hub -> Option B

4. Quick Check:

   Deprecated --link causes node-hub connection fail [OK]

Hint: Avoid deprecated --link; use network for node-hub [OK]

Common Mistakes:

• Assuming Chrome is missing inside node container
• Ignoring hub container status
• Not checking Docker daemon status

5. You want to run tests on Chrome and Firefox browsers simultaneously using Docker Selenium Grid. Which setup is correct?

hard

A. Start hub container, then start both selenium/node-chrome and selenium/node-firefox containers connected to the hub network

B. Start only selenium/node-chrome container; Firefox tests will run on Chrome node

C. Start hub container and run tests locally without nodes

D. Start selenium/node-firefox container first, then hub container

Solution

1. Step 1: Understand multi-browser setup

   To run tests on multiple browsers, you must start the hub and connect nodes for each browser to the hub's network.

2. Step 2: Evaluate options

   Start hub container, then start both selenium/node-chrome and selenium/node-firefox containers connected to the hub network correctly starts hub and both browser nodes connected properly. Start only selenium/node-chrome container; Firefox tests will run on Chrome node misses Firefox node, A misses nodes, and D starts nodes before hub which is incorrect.

3. Final Answer:

   Start hub container, then start both selenium/node-chrome and selenium/node-firefox containers connected to the hub network -> Option A

4. Quick Check:

   Hub + all browser nodes connected = multi-browser tests [OK]

Hint: Start hub first, then all browser nodes on same network [OK]

Common Mistakes:

• Starting nodes before hub
• Running tests without nodes
• Assuming one node can run all browsers