Grid architecture (hub and node) in Selenium Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the role of the Hub in Selenium Grid

In Selenium Grid architecture, what is the primary role of the Hub?

A It acts as a central point to receive test requests and distribute them to registered Nodes.

B It manages test scripts and executes them directly on browsers.

C It stores browser drivers and installs them on Nodes automatically.

D It monitors network traffic between Nodes and external servers.

💡 Hint

Think about which component directs tests to different machines.

The Hub acts as the central server that receives test requests and routes them to the appropriate Nodes based on browser and platform availability.

❓ Predict Output

intermediate

Output of Node registration log snippet

Given the following Node registration log snippet, what is the expected output message indicating successful registration?

Selenium Python

2024-06-01 10:00:00 INFO Selenium Grid Node: Registering to the Hub at http://localhost:4444
2024-06-01 10:00:01 INFO Selenium Grid Node: Registered successfully with session limit 5

A Selenium Grid Node: Session limit exceeded

B Selenium Grid Node: Registration failed due to timeout

C Selenium Grid Node: Hub not reachable at http://localhost:4444

D Selenium Grid Node: Registered successfully with session limit 5

💡 Hint

Look for the message that confirms successful registration.

The log line 'Registered successfully with session limit 5' confirms the Node has connected to the Hub properly.

❓ locator

advanced

Best locator strategy for Node status in Selenium Grid UI

In the Selenium Grid console web UI, which locator strategy is best to find the status element of a Node that has an attribute data-node-id with value node123?

A By.css_selector("div[data-node-id='node123'] .status")

B By.id("status-node123")

C By.xpath("//div[@data-node-id='node123']//span[@class='status']")

D By.class_name("node-status")

💡 Hint

Use attribute selectors for precise targeting.

Using a CSS selector with the attribute data-node-id is precise and less brittle than relying on IDs or classes that may change.

❓ assertion

advanced

Valid assertion to verify Node availability in Selenium Grid

Which assertion correctly verifies that a Node is available and ready to accept sessions in a Selenium Grid test script?

Selenium Python

node_status = driver.find_element(By.CSS_SELECTOR, "div[data-node-id='node123'] .status").text

A assert node_status != "Ready", f"Node should not be ready"

B assert node_status == "Ready", f"Expected 'Ready' but got {node_status}"

C assert node_status is None, "Node status should be None"

D assert node_status == "Offline", "Node is offline"

💡 Hint

Check for the exact status text that means the Node is ready.

The status text 'Ready' indicates the Node is available. The assertion confirms this expected state.

🔧 Debug

expert

Debugging Node connection failure in Selenium Grid

A Node fails to register with the Hub and logs the error: ConnectionRefusedError: [Errno 111] Connection refused. Which is the most likely cause?

A The test script has syntax errors causing Node failure.

B The Node has an incorrect browser driver version installed.

C The Hub server is not running or not reachable at the specified URL.

D The Node's session limit is exceeded.

💡 Hint

Connection refused usually means no server is listening at the address.

This error means the Node cannot connect to the Hub because the Hub is down or the URL is wrong.