Executing JavaScript in Selenium Java - Test Execution Trace

Test Overview

This test opens a web page, executes JavaScript to change the page title, and verifies the title was updated correctly.

Test Code - JUnit with Selenium WebDriver

Selenium Java

import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

public class ExecuteJavaScriptTest {
    private WebDriver driver;

    @BeforeEach
    public void setUp() {
        driver = new ChromeDriver();
    }

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

    @Test
    public void testChangeTitleWithJavaScript() {
        driver.get("https://example.com");
        JavascriptExecutor js = (JavascriptExecutor) driver;
        js.executeScript("document.title = 'New Title';");
        String title = driver.getTitle();
        assertEquals("New Title", title);
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts and Chrome browser opens	Browser window is open but no page loaded yet	—	PASS
2	Navigates to https://example.com	Page https://example.com is loaded with default title 'Example Domain'	—	PASS
3	Executes JavaScript to change document title to 'New Title'	Page title is now 'New Title'	—	PASS
4	Retrieves the page title using driver.getTitle()	Page title retrieved as 'New Title'	Check if title equals 'New Title'	PASS
5	Test ends and browser closes	Browser window closed	—	PASS

Failure Scenario

Failing Condition: JavaScript execution fails or title does not update as expected

Execution Trace Quiz - 3 Questions

What does the JavaScript code in this test do?

A Fills a form input

B Changes the page title to 'New Title'

C Clicks a button on the page

D Reloads the page

Key Result

Use JavascriptExecutor in Selenium to run JavaScript code directly in the browser when standard WebDriver methods cannot perform the needed action.

Practice

1. What is the main purpose of using JavascriptExecutor in Selenium Java?

easy

A. To locate elements on the page using JavaScript selectors

B. To execute JavaScript code directly in the browser during a test

C. To start the Selenium WebDriver session

D. To generate test reports automatically

Solution

1. Step 1: Understand the role of JavascriptExecutor

   JavascriptExecutor allows running JavaScript code inside the browser from Selenium tests.

2. Step 2: Identify the main use case

   It is mainly used to perform actions or retrieve information that Selenium WebDriver cannot do directly.

3. Final Answer:

   To execute JavaScript code directly in the browser during a test -> Option B

4. Quick Check:

   JavascriptExecutor runs JS code in browser [OK]

Hint: Remember: JavascriptExecutor runs JS code inside browser [OK]

Common Mistakes:

• Confusing JavascriptExecutor with element locators
• Thinking it starts WebDriver sessions
• Assuming it generates reports

2. Which of the following is the correct way to cast a WebDriver instance to JavascriptExecutor in Selenium Java?

easy

A. JavascriptExecutor js = driver.executeScript();

B. JavascriptExecutor js = driver.getJavascriptExecutor();

C. JavascriptExecutor js = new JavascriptExecutor(driver);

D. JavascriptExecutor js = (JavascriptExecutor) driver;

Solution

1. Step 1: Recall the casting syntax in Java

   To use JavascriptExecutor, you cast the WebDriver instance like this: (JavascriptExecutor) driver.

2. Step 2: Check each option

   JavascriptExecutor js = (JavascriptExecutor) driver; uses correct casting syntax. The other options are invalid method calls or constructors.

3. Final Answer:

   JavascriptExecutor js = (JavascriptExecutor) driver; -> Option D

4. Quick Check:

   Cast driver to JavascriptExecutor using (JavascriptExecutor) [OK]

Hint: Casting uses (JavascriptExecutor) before driver [OK]

Common Mistakes:

• Using non-existent methods like getJavascriptExecutor()
• Trying to instantiate JavascriptExecutor with new keyword
• Calling executeScript() without casting

3. What will be the output of the following code snippet?

JavascriptExecutor js = (JavascriptExecutor) driver;
String title = (String) js.executeScript("return document.title;");
System.out.println(title);

medium

A. Prints the current page's title

B. Throws a ClassCastException

C. Prints 'undefined'

D. Prints the URL of the page

Solution

1. Step 1: Understand the JavaScript executed

   The script returns document.title, which is the page's title as a string.

2. Step 2: Check the casting and output

   The returned object is cast to String and printed, so it outputs the page title.

3. Final Answer:

   Prints the current page's title -> Option A

4. Quick Check:

   executeScript returns document.title string [OK]

Hint: executeScript returns JS value; cast to String for title [OK]

Common Mistakes:

• Expecting URL instead of title
• Not casting return value to String
• Confusing output with undefined or errors

4. Identify the error in the following code snippet:

JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript("arguments[0].click();");

medium

A. Incorrect casting of driver to JavascriptExecutor

B. executeScript method does not exist

C. Missing WebElement argument to click()

D. JavaScript syntax error in the string

Solution

1. Step 1: Analyze the executeScript call

   The script uses arguments[0].click(); which requires a WebElement passed as an argument.

2. Step 2: Check the method call parameters

   No WebElement is passed to executeScript, so it will fail at runtime.

3. Final Answer:

   Missing WebElement argument to click() -> Option C

4. Quick Check:

   arguments[0] needs a WebElement passed [OK]

Hint: Pass WebElement as argument when using arguments[0] [OK]

Common Mistakes:

• Forgetting to pass WebElement argument
• Assuming casting is wrong
• Thinking executeScript method is missing

5. You want to scroll a page to a specific WebElement using JavaScript in Selenium Java. Which code snippet correctly achieves this?

hard

A. js.executeScript("arguments[0].scrollIntoView(true);", element);

B. js.executeScript("window.scrollTo(element);");

C. js.executeScript("scrollToElement(arguments[0]);", element);

D. js.executeScript("document.scrollTo(arguments[0]);");

Solution

1. Step 1: Recall JavaScript method to scroll to element

   The correct JS method is scrollIntoView(true) called on the element.

2. Step 2: Check the Selenium executeScript usage

   Pass the WebElement as an argument and use arguments[0].scrollIntoView(true); to scroll.

3. Final Answer:

   js.executeScript("arguments[0].scrollIntoView(true);", element); -> Option A

4. Quick Check:

   Use scrollIntoView with element argument [OK]

Hint: Use arguments[0].scrollIntoView(true) with element [OK]

Common Mistakes:

• Using window.scrollTo with element (invalid)
• Calling non-existent scrollToElement function
• Not passing element as argument