Performance metrics via DevTools in Selenium Java - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable performance logging in Selenium WebDriver.

Selenium Java

LoggingPreferences logPrefs = new LoggingPreferences();
logPrefs.enable(LogType.PERFORMANCE, [1]);
ChromeOptions options = new ChromeOptions();
options.setCapability(CapabilityType.LOGGING_PREFS, logPrefs);

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

ALevel.SEVERE

BLevel.OFF

CLevel.ALL

DLevel.WARNING

Attempts:

3 left

💡 Hint

Common Mistakes

Using Level.OFF disables logging, so no performance data is captured.

Using Level.SEVERE or Level.WARNING captures only errors or warnings, missing detailed metrics.

Level.ALL enables capturing all performance logs, which is needed to collect detailed metrics.

2fill in blank

medium

Complete the code to retrieve performance logs from the WebDriver.

Selenium Java

LogEntries performanceLogs = driver.manage().logs().get([1]);

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

ALogType.PERFORMANCE

BLogType.DRIVER

CLogType.BROWSER

DLogType.CLIENT

Attempts:

3 left

💡 Hint

Common Mistakes

Using LogType.BROWSER returns console logs, not performance metrics.

Using LogType.DRIVER or LogType.CLIENT returns unrelated logs.

LogType.PERFORMANCE is used to get performance-related logs from the browser.

3fill in blank

hard

Fix the error in the code to parse performance log entries correctly.

Selenium Java

for (LogEntry entry : performanceLogs) {
    String message = entry.getMessage();
    JsonObject json = JsonParser.parseString(message).getAsJsonObject();
    JsonObject [1] = json.getAsJsonObject("message");
    // process jsonMessage
}

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

AjsonEntry

BjsonMessage

CjsonLog

DjsonData

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names that do not match the JSON structure can cause confusion.

Using undefined variable names leads to compilation errors.

The variable name jsonMessage matches the intended usage and is clear for the parsed message object.

4fill in blank

hard

Fill in the blank to filter performance logs for 'Network.responseReceived' events.

Selenium Java

for (LogEntry entry : performanceLogs) {
    String message = entry.getMessage();
    JsonObject json = JsonParser.parseString(message).getAsJsonObject();
    JsonObject jsonMessage = json.getAsJsonObject("message");
    if (jsonMessage.get("method").getAsString().[1]("Network.responseReceived")) {
        // process network response
    }
}

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

Aequals

Bcontains

CstartsWith

DendsWith

Attempts:

3 left

💡 Hint

Common Mistakes

Using contains or startsWith might match unintended events.

Using endsWith will not match the full event name.

We check if the 'method' exactly equals 'Network.responseReceived' to filter the correct events.

5fill in blank

hard

Fill all three blanks to extract the response URL and status code from performance logs.

Selenium Java

JsonObject params = jsonMessage.getAsJsonObject([1]);
JsonObject response = params.getAsJsonObject([2]);
int status = response.get([3]).getAsInt();

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

A"params"

B"response"

C"status"

D"request"

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect keys like 'request' instead of 'response' causes errors.

Missing quotes around keys leads to syntax errors.

The 'params' object contains 'response', which has the 'status' field for HTTP status code.

Practice

1. What is the main purpose of using DevTools performance metrics in Selenium Java tests?

easy

A. To handle browser alerts automatically

B. To locate elements on the web page

C. To take screenshots during test execution

D. To measure page load speed and browser performance

Solution

1. Step 1: Understand DevTools role in Selenium

   DevTools integration allows Selenium to collect browser performance data like load times.

2. Step 2: Identify the purpose of performance metrics

   Performance metrics help measure page speed and resource usage to improve user experience.

3. Final Answer:

   To measure page load speed and browser performance -> Option D

4. Quick Check:

   Performance metrics = page speed measurement [OK]

Hint: Performance metrics measure speed, not element location [OK]

Common Mistakes:

• Confusing performance metrics with element locators
• Thinking DevTools handles alerts
• Assuming screenshots are related to performance

2. Which Java code snippet correctly enables performance monitoring using DevTools in Selenium?

easy

A. devTools.send(Performance.enable());

B. driver.get("https://example.com");

C. driver.manage().timeouts().pageLoadTimeout(Duration.ofSeconds(10));

D. devTools.send(Network.enable(Optional.empty(), Optional.empty(), Optional.empty()));

Solution

1. Step 1: Identify the correct DevTools command for performance

   The Performance domain in DevTools is enabled by calling Performance.enable().

2. Step 2: Check other options for correctness

   devTools.send(Network.enable(Optional.empty(), Optional.empty(), Optional.empty())); enables Network, not Performance. driver.manage().timeouts().pageLoadTimeout(Duration.ofSeconds(10)); sets timeout, and B loads a page.

3. Final Answer:

   devTools.send(Performance.enable()); -> Option A

4. Quick Check:

   Enable performance with Performance.enable() [OK]

Hint: Use Performance.enable() to start performance monitoring [OK]

Common Mistakes:

• Using Network.enable() instead of Performance.enable()
• Confusing timeout settings with performance enabling
• Calling driver.get() instead of enabling metrics

3. Given the following code snippet, what will be the output type of metrics.getMetrics()?

DevTools devTools = driver.getDevTools();
devTools.createSession();
devTools.send(Performance.enable());
PerformanceMetrics metrics = devTools.send(Performance.getMetrics());
System.out.println(metrics.getMetrics().get(0).getName());

medium

A. A boolean indicating if metrics are enabled

B. An integer value of the first metric

C. A String representing the name of the first performance metric

D. A list of WebElement objects

Solution

1. Step 1: Understand Performance.getMetrics() return type

   It returns a PerformanceMetrics object containing a list of Metric objects, each with a name and value.

2. Step 2: Analyze metrics.getMetrics().get(0).getName()

   This accesses the first Metric's name, which is a String describing the metric.

3. Final Answer:

   A String representing the name of the first performance metric -> Option C

4. Quick Check:

   getName() returns String metric name [OK]

Hint: getName() returns metric name as String, not value [OK]

Common Mistakes:

• Assuming getName() returns a number
• Confusing metrics with WebElements
• Expecting a boolean from getMetrics()

4. Identify the error in this Selenium Java code snippet that tries to enable performance metrics:

DevTools devTools = driver.getDevTools();
devTools.send(Performance.enable());
devTools.createSession();

medium

A. Performance.enable() requires parameters

B. createSession() must be called before sending commands

C. DevTools cannot be used with ChromeDriver

D. No error, code is correct

Solution

1. Step 1: Check the order of DevTools commands

   Session must be created before sending any DevTools commands like Performance.enable().

2. Step 2: Verify method usage

   Calling Performance.enable() before createSession() causes an error because no session exists yet.

3. Final Answer:

   createSession() must be called before sending commands -> Option B

4. Quick Check:

   Call createSession() first, then enable performance [OK]

Hint: Always createSession() before sending DevTools commands [OK]

Common Mistakes:

• Calling enable() before createSession()
• Thinking Performance.enable() needs parameters
• Assuming DevTools is unsupported in ChromeDriver

5. You want to measure the page load time using Selenium Java and DevTools. Which approach correctly captures the 'DomContentLoaded' metric after page load?

hard

A. Enable performance, load page, then get metrics and filter for 'DomContentLoaded'

B. Load page first, then enable performance and get metrics immediately

C. Enable performance, get metrics before loading page, then load page

D. Only use driver.manage().timeouts().pageLoadTimeout() to measure load time

Solution

1. Step 1: Enable performance monitoring before page load

   Performance must be enabled before loading the page to capture all metrics during load.

2. Step 2: Load the page and then retrieve metrics filtering for 'DomContentLoaded'

   After page load, get metrics and select the 'DomContentLoaded' metric to measure load time.

3. Final Answer:

   Enable performance, load page, then get metrics and filter for 'DomContentLoaded' -> Option A

4. Quick Check:

   Enable first, load page, then get metrics [OK]

Hint: Enable before load, get metrics after load for accurate timing [OK]

Common Mistakes:

• Enabling performance after page load misses metrics
• Getting metrics before loading page
• Relying only on timeout settings for load time