Alerts Windows Frames - borzykin/wiki GitHub Wiki

Alert alert = driver.switchTo().alert();
String alertText = alert.getText();
alert.accept();
// либо alert.dismiss();

String mainWindow = driver.getWindowHandle();
Set<String> oldWindows = driver.getWindowHandles();
String newWindow = wait.until(thereIsWindowOtherThan(oldWindows));
driver.switchTo().window(newWindow);

WebDriver.Window window = driver.manage().window();
window.maximize();
window.setSize(new Dimension(800, 600));

driver.switchTo().frame(driver.findElement(By.tagName("iframe")));
driver.switchTo().defaultContent();