Selenium is an open-source automation testing framework for web applications. Main features: cross-browser support, multiple language bindings (Java, Python, C#, Ruby), supports desktop and mobile browsers, can test dynamic content, and has a large community.

Selenium IDE (record and playback), Selenium RC (deprecated), Selenium WebDriver (primary tool for automation), and Selenium Grid (distributed testing). WebDriver is the most commonly used component.

WebDriver is an API that controls a web browser. It sends commands to a web driver server (like ChromeDriver), which then controls the browser. It provides methods to interact with elements and validate behavior.

For Java: add selenium-java dependency to pom.xml (Maven) or build.gradle (Gradle). Download WebDriver executable (ChromeDriver, GeckoDriver for Firefox). Set system property: System.setProperty("webdriver.chrome.driver", "path/to/chromedriver").

For Chrome: WebDriver driver = new ChromeDriver(); For Firefox: WebDriver driver = new FirefoxDriver(); For Safari: WebDriver driver = new SafariDriver();

WebDriver controls the browser and navigates to URLs. WebElement represents an HTML element on the page and allows interaction (click, type, etc.).

Use driver.findElement() or driver.findElements(). Locator strategies: By.id(), By.name(), By.className(), By.tagName(), By.cssSelector(), By.xpath(). Example: driver.findElement(By.id("username"));

findElement() returns a single WebElement (throws NoSuchElementException if not found). findElements() returns a List of WebElements (returns empty list if not found).

Common interactions: .click() (click element), .sendKeys(text) (type text), .submit() (submit form), .clear() (clear input), .getAttribute(attrName) (get attribute value).

XPath is a query language for XML/HTML: //button[@id="submit"]. CSS Selectors target HTML using CSS: button#submit. Both are powerful locators; CSS is generally faster.

Use driver.navigate() or driver.get(). driver.get(url) loads a URL. driver.navigate().to(url) is similar. driver.navigate().back() goes to previous page. driver.navigate().forward() goes to next page. driver.navigate().refresh() reloads page.

Waits handle timing issues. Implicit waits: driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS); (applies to all commands). Explicit waits: WebDriverWait with Expected Conditions for specific elements.

Implicit waits apply to all element searches globally. Explicit waits target specific elements and conditions. Explicit waits are recommended for better control.

Use WebDriverWait: WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(10)); WebElement element = wait.until(ExpectedConditions.visibilityOfElementLocated(By.id("myElement")));

visibilityOfElementLocated(), presenceOfElementLocated(), elementToBeClickable(), invisibilityOfElementLocated(), stalenessOfElement(), textToBePresentInElement().

Use Select class: Select select = new Select(driver.findElement(By.id("dropdown"))); select.selectByValue("value"); or selectByVisibleText("text");

Switch to alert: Alert alert = driver.switchTo().alert(); Accept: alert.accept(); Dismiss: alert.dismiss(); Get text: alert.getText(); Send keys: alert.sendKeys("text");

Get window handles: Set<String> handles = driver.getWindowHandles(); Switch to window: driver.switchTo().window(handle);

Switch to iframe by id/name: driver.switchTo().frame("frameName"); Or by element: driver.switchTo().frame(element); Switch back to main content: driver.switchTo().defaultContent();

switchTo() allows switching context: .window() for windows, .alert() for alerts, .frame() for iframes, .activeElement() for focused element.

Use JavaScriptExecutor: JavaScriptExecutor js = (JavaScriptExecutor) driver; js.executeScript("javascript code", arguments); For example: js.executeScript("arguments[0].scrollIntoView(true);", element);

POM is a design pattern where pages are represented as classes. Each page has methods for interactions. Improves maintainability and reusability. Example: class LoginPage { WebElement username; void login(user, pass) {} }

Use logging frameworks like Log4j or SLF4j. Add logger: private static Logger logger = LoggerFactory.getLogger(TestClass.class); Log statements: logger.info("Test started");

Test frameworks organize tests. Popular: TestNG (annotations, parallel execution, reporting), JUnit (simpler, good for unit tests). TestNG is preferred for Selenium automation.

Use annotations: @BeforeClass (setup), @Test (test method), @AfterClass (teardown). Example: @Test public void loginTest() { ... }

Use TakesScreenshot: File srcFile = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE); FileUtils.copyFile(srcFile, new File("path/screenshot.png"));

Assertions verify expected vs actual values. Examples: Assert.assertEquals(expected, actual); Assert.assertTrue(condition); Assert.fail("message"); From org.testng.Assert.

Common exceptions: NoSuchElementException (element not found), TimeoutException (wait timeout), StaleElementReferenceException (element no longer attached to DOM). Handle with try-catch.

Selenium Grid allows parallel test execution across multiple machines and browsers. Advantages: faster test execution, cross-browser testing, load distribution.

Start hub: java -jar selenium-server.jar hub. Start node: java -jar selenium-server.jar node -hub http://hubIP:4444. Connect via: new RemoteWebDriver(new URL("http://hubIP:4444"), capabilities);

DesiredCapabilities specifies browser properties: DesiredCapabilities caps = new DesiredCapabilities("chrome", "90", Platform.WINDOWS); Includes browser type, version, platform.

Use ChromeOptions or FirefoxOptions: ChromeOptions options = new ChromeOptions(); options.addArguments("--headless"); driver = new ChromeDriver(options);

Headless mode runs browser without GUI. Faster execution, useful for CI/CD. Enable: options.addArguments("--headless");

Use explicit waits with ExpectedConditions. Avoid Thread.sleep() as it's hard-coded and unreliable. Use FluentWait for custom conditions.

Absolute XPath starts from root: /html/body/div/button. Relative XPath starts from element: //button[@id="submit"]. Relative is more maintainable.

XPath: //*[text()="Click me"] or //*[contains(text(), "Click")]. Can combine with tag: //button[text()="Submit"].

Implicit: global timeout for all commands. Explicit: specific wait for specific elements. Mixing both can cause issues; prefer explicit waits.

Use assertion: Assert.assertTrue(driver.findElement(By.id("element")).isDisplayed()); Or wait: wait.until(ExpectedConditions.visibilityOfElementLocated(locator));

WebElement element = driver.findElement(locator); String text = element.getText();

String value = element.getAttribute("attributeName"); Example: element.getAttribute("placeholder");

Check: element.click(); Verify checked: Assert.assertTrue(element.isSelected()); Uncheck: if (element.isSelected()) element.click();

Similar to checkboxes: element.click() to select. Verify: Assert.assertTrue(element.isSelected()); Only one radio button in group can be selected.

Find input type="file" and use sendKeys with absolute file path: driver.findElement(By.id("fileInput")).sendKeys("/absolute/path/to/file.txt");

driver.navigate().refresh(); Or using F5 key: driver.findElement(By.tagName("body")).sendKeys(Keys.F5);

Scroll to element: JavaScriptExecutor js = (JavaScriptExecutor) driver; js.executeScript("arguments[0].scrollIntoView(true);", element);

Capabilities caps = ((RemoteWebDriver) driver).getCapabilities(); String browserName = caps.getBrowserName();

WebDriverManager manages WebDriver executables automatically. No need to manually download drivers: WebDriverManager.chromedriver().setup();

Use @Test with threadPoolSize in testng.xml: <suite parallel="tests" thread-count="3">

Extend ExpectedCondition: public class CustomCondition implements ExpectedCondition<WebElement> { ... }

Use external files (Excel, CSV, JSON) or databases. Read data before test and pass to @DataProvider. Allows running same test with multiple data sets.

FluentWait is customizable: FluentWait<WebDriver> wait = new FluentWait<>(driver).withTimeout(Duration.ofSeconds(10)).pollingEvery(Duration.ofMillis(500)).ignoring(NoSuchElementException.class);

Occurs when element reference is no longer in DOM. Causes: page refresh, element removed/hidden. Solution: re-locate element or use explicit wait.

Use explicit waits for dynamic elements. Wait for element to be visible, clickable, or text to change. Use presence checks before interactions.

Actions class performs complex user interactions: mouse hover, drag-drop, double click. Example: new Actions(driver).moveToElement(element).click().perform();

Actions actions = new Actions(driver); actions.moveToElement(element).perform(); Then interact with revealed element.

Actions actions = new Actions(driver); actions.dragAndDrop(sourceElement, targetElement).perform();

Actions actions = new Actions(driver); actions.doubleClick(element).perform();

Actions actions = new Actions(driver); actions.contextClick(element).perform(); Then interact with context menu.

Use Keys enum: Keys.TAB, Keys.ENTER, Keys.ESCAPE. Example: element.sendKeys(Keys.CONTROL + "A"); (select all)

Robot class simulates keyboard/mouse at OS level (not within browser). Use for system dialogs, file downloads. Example: Robot robot = new Robot(); robot.keyPress(KeyEvent.VK_ENTER);

Methods return WebElement or WebDriver: driver.findElement(locator).click(); Can chain: driver.findElement(locator).sendKeys("text").submit();

Assert.assertTrue(element.isEnabled()); Or: Assert.assertFalse(element.isEnabled()); (for disabled)

String value = element.getCssValue("propertyName"); Example: element.getCssValue("color") returns computed color.

Create retry method: boolean retryCount = 0; while(retryCount < 3) { try { doAction(); break; } catch (Exception e) { retryCount++; } }

@FindBy(id="elementId") WebElement element; Automatically initializes elements: PageFactory.initElements(driver, this);

Use @DataProvider: @DataProvider public Object[][] getData() { return new Object[][]{ {data1}, {data2} }; } Then: @Test(dataProvider="getData") void test(String data) {}

Use Apache POI: XSSFWorkbook workbook = new XSSFWorkbook(new File("file.xlsx")); XSSFSheet sheet = workbook.getSheetAt(0); Cell cell = sheet.getRow(0).getCell(0);

Use OpenCSV or manual parsing: BufferedReader br = new BufferedReader(new FileReader("file.csv")); String[] values = br.readLine().split(",");

Use parameters in testng.xml or @Parameters: @Parameters({"browser"}) @Test void test(String browser) { driver = initDriver(browser); }

BaseTest contains common setup/teardown logic. All test classes extend it: public class LoginTest extends BaseTest { ... }

Create listener class implementing ITestListener, IInvokedMethodListener. Override methods: onTestStart(), onTestSuccess(), onTestFailure().

Add allure-testng dependency. Configure @Step annotations. Generate: allure generate target/allure-results -o allure-report

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

Get cookie: Cookie cookie = driver.manage().getCookie("name"); Check: Assert.assertNotNull(cookie);

Add: driver.manage().addCookie(new Cookie("name", "value")); Delete: driver.manage().deleteCookie("name");

Create Dockerfile with Chrome/Firefox and Selenium. Build image and run container. Useful for CI/CD pipelines.

Store config values (URLs, credentials). Use System.getenv() or properties files. Avoid hardcoding sensitive data.

Use Log4j: Logger logger = LoggerFactory.getLogger(TestClass.class); logger.info("Message"); Configure via log4j.properties.

Set timeouts in options: options.setPageLoadTimeout(30, TimeUnit.SECONDS); options.setImplicitlyWait(10, TimeUnit.SECONDS);

Use HttpClient or RestTemplate (not Selenium native). Send requests and verify responses. Selenium is for UI testing; use dedicated API testing tools.

Extend TestNG, add BaseTest class, implement listeners, create utilities. Define test structure and standards.

Use navigation timing: JavaScriptExecutor js = (JavaScriptExecutor) driver; Long loadTime = (Long) js.executeScript("return window.performance.timing.loadEventEnd - window.performance.timing.navigationStart;");

Navigate directly: driver.get("https://example.com/nonexistent"); Verify error message: Assert.assertEquals(driver.getTitle(), "404 Not Found");

Create testng.xml with multiple suite tags or test tags. Run specific suite: mvn test -Dsuite=testng.xml

Use SoftAssert: SoftAssert softAssert = new SoftAssert(); softAssert.assertEquals(actual, expected); softAssert.assertAll(); (reports all failures at end)

Get window handles: Set<String> handles = driver.getWindowHandles(); Switch to popup: driver.switchTo().window(newHandle);

Use Page Object Model with login methods. Store credentials in properties files. Use cy.session() equivalent (login once, reuse session).

Set viewport size: driver.manage().window().setSize(new Dimension(375, 667)); Verify responsive layout changes.

XPath: //*[parent[@id="parent"]]/child or //parent//child. CSS: parent > child or parent child.

Assert.assertTrue(driver.getCurrentUrl().contains("/dashboard")); Or: Assert.assertTrue(driver.getCurrentUrl().matches(".*\\/dashboard.*"));

XPath: //label[text()="Email"]/..//input or //label[contains(text(), "Email")]/following::input

Find table rows: List<WebElement> rows = driver.findElements(By.xpath("//table//tr")); Extract cell data: row.findElements(By.xpath(".//td"));

element.sendKeys(Keys.chord(Keys.CONTROL, "a")); (select all) element.sendKeys(Keys.chord(Keys.SHIFT, "a")); (uppercase A)

Hard to test printing directly. Verify print button presence: Assert.assertTrue(driver.findElement(By.id("printBtn")).isDisplayed());

Type in input: element.sendKeys("text"); Wait for suggestions: wait.until(ExpectedConditions.presenceOfAllElementsLocatedBy(By.xpath("//suggestion")));

List<WebElement> elements = driver.findElements(By.className("item")); Iterate: for (WebElement elem : elements) { }

Assert.assertEquals(driver.findElements(By.className("item")).size(), 5);

List<WebElement> items = driver.findElements(locator); WebElement lastItem = items.get(items.size() - 1);

Assert.assertTrue(element.getText().contains("partial text")); Or: Assert.assertTrue(element.getText().matches(".*pattern.*"));

For input type="date": element.sendKeys("12122025"); For calendar widgets: click date picker, click desired date.

Parallelize tests, use headless mode, minimize waits, cache data, avoid unnecessary scrolls, use fast selectors (ID/class over XPath), implement connection pooling.

Use Cucumber/BDD to write tests in Gherkin (plain English). Bridges gap between QA and business. Feature files describe scenarios, step definitions implement them.

Add cucumber-java dependency. Write .feature files with Gherkin syntax. Create StepDefinitions class: @Given("user is on login page") public void loginPage() {}

@Before runs before each scenario, @After runs after. Used for setup/teardown: @Before public void setUp() { driver = new ChromeDriver(); }

Use frameworks like Spring or PicoContainer. Inject WebDriver and PageObjects: @Autowired private WebDriver driver;

Test offline functionality, service workers, app shell. Use browser DevTools APIs via JavaScriptExecutor. Test responsive design and installation prompts.

Store JWT in localStorage/sessionStorage. Use JavaScriptExecutor: js.executeScript("localStorage.setItem('token', '" + jwtToken + "');");

Use HttpClient or RestTemplate to send GraphQL requests. Not Selenium-specific; use dedicated API testing tools for comprehensive GraphQL testing.

Shadow DOM encapsulates styles and markup. Hard to access via normal selectors. Use JavaScriptExecutor to pierce shadow DOM or use specialized selectors if available.

Interact via public APIs or exposed attributes. Use JavaScriptExecutor to interact with component properties: js.executeScript("document.querySelector('custom-elem').setAttribute('prop', 'value');");

Integrate tests in Jenkins/GitHub Actions. Run tests on each commit. Configure test execution, reporting, notifications.

Generate reports (Allure, ExtentReports), attach screenshots/logs. Analyze logs for errors, timeouts, environment issues. Setup alerts for failures.

Identify root causes (timing, network, unstable selectors). Implement retry logic, improve waits, stabilize selectors. Use data-testid attributes.

Use Selenium Grid or cloud services (BrowserStack, Sauce Labs). Configure parallel execution on different browsers and OS combinations.

Test same functionality on different OS (Windows, Mac, Linux). Use Selenium Grid with nodes on different platforms.

Use Chrome DevTools Protocol (CDP) via Selenium 4. Or mock features via JavaScriptExecutor for testing UI behavior.

Use tools like Applitools Eyes, Percy, or visual regression libraries. Compare screenshots with baseline images.

Use Axe-Core plugin: axe.analyze((results) => { assert(results.violations.length === 0); });

Use Navigation Timing API: js.executeScript("return window.performance.timing");. Verify load time, FCP, LCP.

Hard to test video/audio streams. Verify player UI and controls instead. Use mock servers for testing without real streams.

Mock API responses via proxies or test double servers. Test UI behavior with different API responses (success, error, timeout).

Extend ExpectedCondition: public class MyWait implements ExpectedCondition<Boolean> { ... } Use with FluentWait.

Use environment variables or config files to enable/disable features. Test both enabled and disabled states.

Create @AfterClass methods to delete test data via API or database. Use transactions that rollback after tests.

Never hardcode passwords/API keys. Use environment variables or secure vaults (HashiCorp Vault, AWS Secrets Manager).

Set locale in Chrome options: options.addArguments("--accept-lang=fr-FR"); Verify UI translates correctly.

Use JavaScriptExecutor to set timezone in browser or OS. Or use TZ environment variable in Docker.

Run tests affected by code changes. Analyze code coverage and test impact. Tools: TestNG, Maven Surefire plugin.

Break into smaller steps, use Page Object Model, implement reusable components. Document flow with BDD/Gherkin.

Capture screenshots/videos, save logs, use remote debugging with BrowserStack/Sauce Labs. Analyze logs and replicate locally.

Use @Test(groups = {"smoke", "regression"}). Run specific groups: mvn test -Dgroups=smoke

Use TestNG reports or custom listeners. Identify slow tests and optimize. Set performance baselines.

Avoid coupling tests. Use @Test(dependsOnMethods = {"testA"}) when necessary. Prefer independent tests.

Focus on UI testing. Mock/stub backend services. Test API contracts separately. Ensure UI works with different service responses.

Create IRetryAnalyzer: public class Retry implements IRetryAnalyzer { ... } Apply to tests: @Test(retryAnalyzer = Retry.class)

136-150. Advanced Topics (abbreviated)

136-140: Distributed testing strategies, test environment setup, test data generation, performance testing, mobile testing. 141-145: Test containerization, test orchestration, AI-powered testing, self-healing tests, smart waits. 146-150: Custom reporting, test metrics, test monitoring, root cause analysis, test ROI.