PrepCampusPlus

What is Selenium? Selenium is an open-source automation testing framework used for validating web applications across different browsers and platforms. It allows testers to write test scripts in multiple programming languages like Java, Python, C#, Ruby, and JavaScript. Selenium is widely recognized for its robustness, flexibility, and extensive community support.

What are the components of Selenium? Selenium is a suite of tools with the following components:

Selenium IDE: A Firefox/Chrome plugin for recording and playback of tests. It is beginner-friendly but limited to simple testing scenarios.
Selenium RC (Remote Control): A tool for writing automated web application UI tests in multiple programming languages. Deprecated in favor of WebDriver.
Selenium WebDriver: A more advanced and robust tool for creating browser-based test automation scripts without relying on a server.
Selenium Grid: A tool used to execute tests in parallel across multiple machines and browsers, enabling distributed testing.

What is Selenium WebDriver? Selenium WebDriver is a web automation framework that allows you to execute tests on different browsers. It provides a programming interface to interact with and control browser elements directly. WebDriver supports dynamic web applications and makes it possible to implement advanced test cases.

What are the differences between Selenium 1 and Selenium 2?

Selenium 1:
- Refers to Selenium RC.
- Uses a server to interact with browsers.
- Less efficient and slower.
Selenium 2:
- Introduced WebDriver, which directly communicates with browsers.
- Faster and more robust.
- Offers better support for dynamic web pages.

What is the difference between Selenium RC and WebDriver?

Aspect	Selenium RC	WebDriver
Architecture	Requires a server to interact with browsers.	Directly communicates with browsers.
Speed	Slower due to server dependency.	Faster and more efficient.
API Simplicity	Complex and outdated.	Simple and intuitive.
Browser Compatibility	Limited support.	Broader support, including modern browsers.

Name the different types of WebDriver.

ChromeDriver
GeckoDriver (FirefoxDriver)
SafariDriver
EdgeDriver
OperaDriver
InternetExplorerDriver
HtmlUnitDriver (headless browser)

What are the major advantages of using Selenium WebDriver?

Supports multiple programming languages.
Works with various browsers and platforms.
Offers detailed control over web elements using locators.
Enables parallel and distributed test execution using Selenium Grid.
Supports headless testing for faster execution.
Open-source and has strong community support.

Can Selenium handle window-based pop-ups? No, Selenium cannot handle window-based pop-ups directly because it is designed to automate web applications. For handling OS-level pop-ups, third-party tools like AutoIt or Robot class in Java can be used.

How do you launch a browser using WebDriver? To launch a browser, you need to:

Set the path of the browser driver executable.
Create an instance of the WebDriver class for the specific browser.

Example in Java for Chrome:

System.setProperty("webdriver.chrome.driver", "path/to/chromedriver");
WebDriver driver = new ChromeDriver();
driver.get("https://example.com");

What is the get() method used for in WebDriver? The get() method is used to navigate to a specific URL in the browser. It waits until the page is fully loaded before proceeding with the next command.

Example:

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

How do you navigate between pages using Selenium WebDriver? The navigate() method provides navigation capabilities:

navigate().to() – To load a new URL.
navigate().back() – To go to the previous page.
navigate().forward() – To move to the next page.
navigate().refresh() – To reload the current page.

Example:

driver.navigate().to("https://example.com");
driver.navigate().back();
driver.navigate().forward();
driver.navigate().refresh();

What are some limitations of Selenium WebDriver?

Cannot automate desktop applications or window-based pop-ups.
Does not provide in-built reporting capabilities.
Limited support for mobile application testing.
Requires external libraries for advanced features like visual testing.
Cannot handle Captcha and OTP verification directly.

Which browsers does Selenium WebDriver support? Selenium WebDriver supports the following browsers:

Google Chrome
Mozilla Firefox
Safari
Microsoft Edge
Internet Explorer
Opera
HtmlUnit (headless browser)

How do you close the current window in Selenium? The close() method is used to close the current active browser window.

Example:

driver.close();

How do you quit all browser windows in Selenium? The quit() method is used to close all browser windows opened during the test session.

Example:

driver.quit();

What is the use of findElement() in Selenium? The findElement() method is used to locate a single web element on the current web page. It returns the first matching element based on the specified locator strategy.

Example:

WebElement element = driver.findElement(By.id("username"));
element.sendKeys("testuser");

What are the types of locators in Selenium?

ID
Name
Class Name
Tag Name
Link Text
Partial Link Text
CSS Selector
XPath

What is an XPath in Selenium? XPath is a powerful locator strategy used to navigate and identify elements in an XML or HTML structure. It allows for precise element selection, even in dynamic web pages.

What is a CSS Selector in Selenium? A CSS Selector is a locator strategy that uses CSS rules to select web elements. It is faster than XPath and widely used for locating elements with specific attributes, classes, or IDs.

What is the difference between absolute XPath and relative XPath?

Absolute XPath:
- Starts from the root node (/).
- Example: /html/body/div[1]/div[2]/a.
- Less robust; breaks with minor DOM changes.
Relative XPath:
- Starts from any node using //.
- Example: //div[@class='example'].
- More flexible and reliable.

How do you handle drop-downs in Selenium? Drop-downs can be handled using the Select class in Selenium.

Example:

Select dropdown = new Select(driver.findElement(By.id("dropdown")));
dropdown.selectByVisibleText("Option 1");

How do you handle frames and iframes in Selenium? Selenium provides the switchTo() method to handle frames and iframes.

Example:

driver.switchTo().frame("frameName");
driver.switchTo().defaultContent();

How do you handle JavaScript alerts in Selenium? Selenium can handle JavaScript alerts using the Alert interface.

Example:

Alert alert = driver.switchTo().alert();
alert.accept();

How do you capture a screenshot in Selenium WebDriver? Screenshots can be captured using the TakesScreenshot interface.

Example:

File screenshot = ((TakesScreenshot) driver).getScreenshotAs(OutputType.FILE);
FileUtils.copyFile(screenshot, new File("screenshot.png"));

What are the implicit and explicit waits in Selenium?

Implicit Wait: Implicit wait is applied globally to the WebDriver instance. It tells WebDriver to poll the DOM for a specified amount of time when trying to find an element. If the element is not found within the specified time, a NoSuchElementException is thrown.

// Example of implicit wait
WebDriver driver = new ChromeDriver();
driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(10));

Explicit Wait: Explicit wait is applied to specific elements. It waits for a certain condition to occur before proceeding with the next step.

// Example of explicit wait
WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
WebElement element = wait.until(ExpectedConditions.visibilityOfElementLocated(By.id("example")));

How do you switch between windows in Selenium?

You can use getWindowHandles() to get all window handles and switchTo().window() to switch between them.

// Example to switch between windows
String mainWindow = driver.getWindowHandle();
Set<String> allWindows = driver.getWindowHandles();

for (String window : allWindows) {
    if (!window.equals(mainWindow)) {
        driver.switchTo().window(window);
    }
}

What is a WebDriverWait in Selenium?

WebDriverWait is used for explicit waits. It waits for a specific condition to occur before proceeding.

WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.elementToBeClickable(By.id("button")));

How do you handle cookies in Selenium?

Cookies can be managed using addCookie, getCookieNamed, deleteCookie, etc.

// Example of handling cookies
Cookie cookie = new Cookie("test", "12345");
driver.manage().addCookie(cookie);
Cookie retrievedCookie = driver.manage().getCookieNamed("test");
driver.manage().deleteCookie(cookie);
driver.manage().deleteAllCookies();

What is the difference between driver.close() and driver.quit()?

driver.close(): Closes the current active window.
driver.quit(): Closes all windows and terminates the WebDriver session.

How do you handle mouse hover actions in Selenium?

Use the Actions class to perform mouse hover actions.

Actions actions = new Actions(driver);
WebElement element = driver.findElement(By.id("hover"));
actions.moveToElement(element).perform();

What is the Actions class in Selenium?

The Actions class is used for handling complex user interactions such as drag-and-drop, mouse hover, and double-click.

How do you perform drag and drop in Selenium?

Use the dragAndDrop() method from the Actions class.

Actions actions = new Actions(driver);
WebElement source = driver.findElement(By.id("source"));
WebElement target = driver.findElement(By.id("target"));
actions.dragAndDrop(source, target).perform();

How do you handle AJAX elements in Selenium?

You can handle AJAX elements using explicit waits to wait for the element’s condition.

WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10));
wait.until(ExpectedConditions.visibilityOfElementLocated(By.id("ajaxElement")));

What is Selenium Grid?

Selenium Grid allows the execution of tests on multiple browsers and operating systems simultaneously.

What is the use of Selenium Grid?

Parallel execution of tests.
Cross-browser testing.
Distributed test execution across multiple machines.

How do you perform parallel testing using Selenium?

You can use Selenium Grid with a hub and multiple nodes or integrate with testing frameworks like TestNG.

<test name="Parallel Tests" parallel="tests" thread-count="2">

What is headless browser testing in Selenium?

Headless browsers run tests without a graphical user interface, improving speed and resource usage.

What is PhantomJS in Selenium?

PhantomJS is a headless browser used for Selenium testing, but it is now deprecated. Use headless modes of Chrome or Firefox instead.

What is the difference between getTitle() and getPageSource() in WebDriver?

getTitle(): Retrieves the page title.
getPageSource(): Retrieves the entire HTML source of the page.

What is the purpose of getWindowHandle() in Selenium?

getWindowHandle() retrieves the handle of the current active window.

What are some exceptions in Selenium?

NoSuchElementException
StaleElementReferenceException
TimeoutException
ElementNotInteractableException

How do you handle NoSuchElementException in Selenium?

Use explicit waits.
Verify the element’s locator and presence in the DOM.

What is the StaleElementReferenceException and how do you handle it?

It occurs when an element is no longer attached to the DOM.

Handling:

Refresh the page.
Re-locate the element.

How do you verify an element is displayed on the page in Selenium?

Use isDisplayed() method.

boolean isVisible = driver.findElement(By.id("example")).isDisplayed();

How do you perform scrolling in Selenium WebDriver?

Use the executeScript() method to perform scrolling.

JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript("window.scrollBy(0,500)");

What is the difference between sendKeys() and clear() methods?

sendKeys(): Inputs text into a field.
clear(): Clears text from a field.

What is the use of the executeScript() method in WebDriver?

executeScript() is used to execute JavaScript commands.

JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript("alert('Hello World')");

Can you use Selenium for performance testing?

Selenium is not ideal for performance testing. Tools like JMeter or Gatling are better suited.

How do you read text from a web page in Selenium?

Use the getText() method.

String text = driver.findElement(By.id("example")).getText();

How do you handle SSL certificate issues in Selenium?

Set the desired capabilities to accept insecure certificates.

ChromeOptions options = new ChromeOptions();
options.setAcceptInsecureCerts(true);
WebDriver driver = new ChromeDriver(options);

What are the locators available in Selenium?

Selenium provides several locators to identify elements on a webpage:

ID: Locates elements using the unique id attribute.
Name: Locates elements by their name attribute.
Class Name: Locates elements by their class attribute.
Tag Name: Locates elements by their HTML tag.
Link Text: Locates anchor elements by their exact visible text.
Partial Link Text: Locates anchor elements by a partial match of their visible text.
CSS Selector: Locates elements using CSS-style syntax.
XPath: Locates elements using XML path expressions.

What is XPath?

XPath (XML Path Language) is a syntax used to navigate through elements and attributes in an XML document. In Selenium, it is widely used to locate elements on a webpage based on their HTML structure.

Syntax:

//tagname[@attribute='value']

Types of XPath:

Absolute XPath: Starts from the root node.
- Example: /html/body/div[1]/input
Relative XPath: Starts from any node in the DOM.
- Example: //input[@id='username']

What is the difference between findElement() and findElements()?

findElement()	findElements()
Returns a single WebElement.	Returns a list of WebElements.
Throws `NoSuchElementException` if the element is not found.	Returns an empty list if no elements are found.
Example: `driver.findElement(By.id("username"));`	Example: `driver.findElements(By.tagName("a"));`

What are the advantages of using CSS selectors?

Faster than XPath: CSS selectors are directly interpreted by browsers.
Simpler Syntax: Easier to write and maintain.
Advanced Patterns: Allows selection using pseudo-classes and combinators.
Works with Dynamic Elements: Handles dynamic classes effectively.

What is an ID locator in Selenium?

ID locator uses the id attribute to identify elements. IDs are unique on a webpage, making it a preferred locator for precision.

Example:

WebElement element = driver.findElement(By.id("username"));

How do you use the name locator in Selenium?

The name locator identifies elements by their name attribute.

Example:

WebElement element = driver.findElement(By.name("email"));

How do you locate an element using its class name in Selenium?

The className locator identifies elements using the class attribute.

Example:

WebElement element = driver.findElement(By.className("form-control"));

What is an absolute XPath in Selenium?

An absolute XPath provides the complete path from the root node to the target element.

Example:

/html/body/div/form/input

Cons:

Prone to breaking with DOM structure changes.

What is a relative XPath in Selenium?

A relative XPath starts from the desired node, not the root node, making it more flexible and robust.

Example:

//input[@id='password']

What is the difference between XPath and CSS selectors in Selenium?

XPath	CSS Selector
Supports both forward and backward traversal.	Supports only forward traversal.
Allows the use of functions like `text()` and `contains()`.	Cannot use text-based search directly.
Slightly slower than CSS.	Faster due to direct browser support.

How do you write XPath for an element containing specific text?

Use the contains() or text() function.

Example:

//button[contains(text(),'Submit')]

How do you find elements by link text in Selenium?

The linkText locator identifies anchor elements by their exact visible text.

Example:

WebElement link = driver.findElement(By.linkText("Home"));

How do you locate an element using partial link text?

The partialLinkText locator identifies anchor elements by a substring of their visible text.

Example:

WebElement link = driver.findElement(By.partialLinkText("Contact"));

What is the By class in Selenium?

The By class is used to define locators in Selenium. It provides methods like id(), name(), xpath(), and cssSelector() to locate elements.

Example:

WebElement element = driver.findElement(By.id("username"));

How do you locate elements by tag name in Selenium?

The tagName locator identifies elements by their HTML tag.

Example:

List<WebElement> links = driver.findElements(By.tagName("a"));

What is the purpose of starts-with in XPath?

The starts-with() function matches elements whose attribute values begin with a specific substring.

Example:

//input[starts-with(@id, 'user')]

What is the use of contains() in XPath?

The contains() function matches elements containing a specific substring in their attribute values or text.

Example:

//div[contains(@class, 'error')]

How do you handle dynamic elements using XPath?

Dynamic elements can be located using:

contains() function.
starts-with() function.
Partial matching of attributes.

Example:

//button[contains(@id, 'submit')]

How do you use the following-sibling axis in XPath?

Selects the next sibling of the current node.

Example:

//label[text()='Username']/following-sibling::input

How do you use preceding-sibling in XPath?

Selects the previous sibling of the current node.

Example:

//input[@id='password']/preceding-sibling::label

How do you use the ancestor axis in XPath?

Selects all ancestor nodes (parent, grandparent, etc.) of the current node.

Example:

//input[@id='username']/ancestor::form

How do you locate child elements using XPath?

The child axis selects immediate children of a node.

Example:

//div[@id='container']/child::input

How do you locate parent elements in XPath?

The parent axis selects the immediate parent of a node.

Example:

//input[@id='username']/parent::div

What is the last() function in XPath?

The last() function selects the last element in a node set.

Example:

//ul/li[last()]

What is the use of position() in XPath?

The position() function selects an element based on its position in a node set.

Example:

//ul/li[position()=2]

How do you locate elements by attributes in CSS selectors?

Attributes are matched using square brackets.

Example:

input[type='text']

How do you find elements that contain a specific substring in CSS selectors?

Use the *= operator.

Example:

div[class*='error']

What is the difference between == and = in XPath?

=: Checks equality of an attribute value.
==: Not valid in XPath.

Example:

//input[@id='username']

XPath and CSS Selectors Interview Guide

1. How do you combine multiple conditions in XPath?

In XPath, multiple conditions can be combined using the and or or operators within square brackets ([]). These are used to filter nodes based on multiple criteria.

Example:

//input[@type='text' and @name='username']

This selects all <input> elements with type='text' and name='username'.

//div[@class='container' or @id='main']

This selects all <div> elements with class='container' or id='main'.

2. How do you use `or` and `and` operators in XPath?

and Operator: Ensures that all specified conditions must be true. Example:
```
//button[@type='submit' and @class='btn-primary']
```
Selects <button> elements that have both type='submit' and class='btn-primary'.
or Operator: Ensures that at least one of the specified conditions must be true. Example:
```
//a[@class='link' or @target='_blank']
```
Selects <a> elements with class='link' or target='_blank'.

3. How do you handle spaces in XPath?

To handle spaces in XPath, you can use the normalize-space() function, which trims leading and trailing spaces and collapses multiple spaces into a single space.

Example:

//div[normalize-space(@class)='header']

This matches <div> elements where the class attribute equals header after removing extra spaces.

4. How do you find the nth element in XPath?

XPath provides the position() function or allows indexing directly with square brackets.

Example:

//ul/li[3]

Selects the third <li> element inside a <ul>.

Using position():

//ul/li[position()=3]

5. What is the `not()` function in XPath?

The not() function in XPath is used to select elements that do not meet a certain condition.

Example:

//input[not(@type='hidden')]

Selects all <input> elements except those with type='hidden'.

6. How do you select elements with a specific attribute value in CSS selectors?

In CSS, you can use attribute selectors to target elements based on specific attribute values.

Syntax:

element[attribute='value']

Example:

input[type='text']

Selects all <input> elements where type='text'.

7. How do you locate elements by index in XPath?

To locate elements by index in XPath, use square brackets with the desired index (1-based).

Example:

(//div[@class='example'])[2]

Selects the second <div> element with class='example'.

8. How do you use pseudo-classes in CSS selectors?

Pseudo-classes in CSS define special states of elements.

Example:

a:hover

Targets links when the user hovers over them.

Common pseudo-classes:

:first-child: Selects the first child of an element.
:nth-child(n): Selects the nth child of an element.
:last-child: Selects the last child of an element.

9. What is the use of `child::` in XPath?

The child:: axis selects child elements of the current node.

Example:

//div/child::p

Selects all <p> elements that are direct children of <div> elements.

10. What is the `self::` axis in XPath?

The self:: axis refers to the context node itself.

Example:

//button[self::button]

Selects <button> elements if the context node is also a <button>.

11. What is the `following::` axis in XPath?

The following:: axis selects all nodes that appear after the current node in the document.

Example:

//h1/following::p

Selects all <p> elements that come after an <h1> element.

12. How do you locate elements with dynamic class names?

For dynamic class names, use partial matching functions like contains() in XPath or substring matching in CSS.

XPath Example:

//*[contains(@class, 'dynamic-part')]

CSS Example:

div[class*='dynamic-part']

13. How do you locate hidden elements in Selenium?

Use the getAttribute() method to check attributes like style, hidden, or aria-hidden.

Example in Java:

WebElement element = driver.findElement(By.xpath("//div[@style='display:none']"));

14. What is the use of CSS selector `nth-child`?

The nth-child pseudo-class selects elements based on their position among siblings.

Example:

ul li:nth-child(3)

Selects the third <li> element within a <ul>.

15. How do you combine class names in CSS selectors?

Combine class names by concatenating them with a period (.).

Example:

div.class1.class2

Selects <div> elements with both class1 and class2.

16. How do you find sibling elements using CSS selectors?

Use the general sibling selector (~) or adjacent sibling selector (+).

Examples:

h1 + p

Selects the <p> element immediately following an <h1>.

h1 ~ p

Selects all <p> elements that are siblings of an <h1>.

17. How do you locate elements with specific text in CSS selectors?

CSS selectors do not natively support text matching. Use XPath for text-based searches:

//*[text()='Specific Text']

18. How do you select the first element of a specific type using CSS?

Use the :first-of-type pseudo-class.

Example:

p:first-of-type

Selects the first <p> element among its siblings.

19. What is the use of the `:nth-of-type` pseudo-class?

The :nth-of-type(n) pseudo-class selects the nth element of a specific type among its siblings.

Example:

div:nth-of-type(2)

Selects the second <div> element among its siblings.

20. How do you select an element that is the last child using CSS?

Use the :last-child pseudo-class.

Example:

li:last-child

Selects the last <li> element within its parent.

21. What is the difference between `:first-child` and `:nth-child(1)` in CSS?

:first-child: Matches the first child of its parent, regardless of type.
:nth-child(1): Matches the first child, but can include specific element types.

Example:

div:first-child

Matches the first child if it is a <div>.

:nth-child(1)

Matches the first child, regardless of its type.

22. How do you select elements with an exact attribute value in CSS selectors?

Use the attribute selector with exact matching:

Syntax:

[name='username']

SideMenu

What are the implicit and explicit waits in Selenium?

How do you switch between windows in Selenium?

What is a WebDriverWait in Selenium?

How do you handle cookies in Selenium?

What is the difference between driver.close() and driver.quit()?

How do you handle mouse hover actions in Selenium?

What is the Actions class in Selenium?

How do you perform drag and drop in Selenium?

How do you handle AJAX elements in Selenium?

What is Selenium Grid?

What is the use of Selenium Grid?

How do you perform parallel testing using Selenium?

What is headless browser testing in Selenium?

What is PhantomJS in Selenium?

What is the difference between getTitle() and getPageSource() in WebDriver?

What is the purpose of getWindowHandle() in Selenium?

What are some exceptions in Selenium?

How do you handle NoSuchElementException in Selenium?

What is the StaleElementReferenceException and how do you handle it?

How do you verify an element is displayed on the page in Selenium?

How do you perform scrolling in Selenium WebDriver?

What is the difference between sendKeys() and clear() methods?

What is the use of the executeScript() method in WebDriver?

Can you use Selenium for performance testing?

How do you read text from a web page in Selenium?

How do you handle SSL certificate issues in Selenium?

What are the locators available in Selenium?

What is XPath?

What is the difference between findElement() and findElements()?

What are the advantages of using CSS selectors?

What is an ID locator in Selenium?

How do you use the name locator in Selenium?

How do you locate an element using its class name in Selenium?

What is an absolute XPath in Selenium?

What is a relative XPath in Selenium?

What is the difference between XPath and CSS selectors in Selenium?

How do you write XPath for an element containing specific text?

How do you find elements by link text in Selenium?

How do you locate an element using partial link text?

What is the By class in Selenium?

How do you locate elements by tag name in Selenium?

What is the purpose of starts-with in XPath?

What is the use of contains() in XPath?

How do you handle dynamic elements using XPath?

How do you use the following-sibling axis in XPath?

How do you use preceding-sibling in XPath?

How do you use the ancestor axis in XPath?

How do you locate child elements using XPath?

How do you locate parent elements in XPath?

What is the last() function in XPath?

What is the use of position() in XPath?

How do you locate elements by attributes in CSS selectors?

How do you find elements that contain a specific substring in CSS selectors?

What is the difference between == and = in XPath?

1. How do you combine multiple conditions in XPath?

2. How do you use or and and operators in XPath?

3. How do you handle spaces in XPath?

4. How do you find the nth element in XPath?

5. What is the not() function in XPath?

6. How do you select elements with a specific attribute value in CSS selectors?

7. How do you locate elements by index in XPath?

8. How do you use pseudo-classes in CSS selectors?

9. What is the use of child:: in XPath?

10. What is the self:: axis in XPath?

11. What is the following:: axis in XPath?

12. How do you locate elements with dynamic class names?

13. How do you locate hidden elements in Selenium?

14. What is the use of CSS selector nth-child?

15. How do you combine class names in CSS selectors?

16. How do you find sibling elements using CSS selectors?

17. How do you locate elements with specific text in CSS selectors?

18. How do you select the first element of a specific type using CSS?

19. What is the use of the :nth-of-type pseudo-class?

20. How do you select an element that is the last child using CSS?

21. What is the difference between :first-child and :nth-child(1) in CSS?

22. How do you select elements with an exact attribute value in CSS selectors?

Use the attribute selector with exact matching:Syntax:[name='username']

🚀 Try Our Free Mock Interviews!

2. How do you use `or` and `and` operators in XPath?

5. What is the `not()` function in XPath?

9. What is the use of `child::` in XPath?

10. What is the `self::` axis in XPath?

11. What is the `following::` axis in XPath?

14. What is the use of CSS selector `nth-child`?

19. What is the use of the `:nth-of-type` pseudo-class?

21. What is the difference between `:first-child` and `:nth-child(1)` in CSS?

Use the attribute selector with exact matching:
Syntax:
`[name='username']`