请基于TESTng框架写一个PO模式的UI自动化测试框架

非常感谢您的提问。我可以回答您的问题。以下是基于TESTng框架的PO模式的UI自动化测试框架的代码示例：

public class LoginPage {
    private WebDriver driver;
    private By usernameLocator = By.id("username");
    private By passwordLocator = By.id("password");
    private By loginButtonLocator = By.id("loginButton");

    public LoginPage(WebDriver driver) {
        this.driver = driver;
    }

    public void setUsername(String username) {
        driver.findElement(usernameLocator).sendKeys(username);
    }

    public void setPassword(String password) {
        driver.findElement(passwordLocator).sendKeys(password);
    }

    public void clickLoginButton() {
        driver.findElement(loginButtonLocator).click();
    }
}

public class HomePage {
    private WebDriver driver;
    private By welcomeMessageLocator = By.id("welcomeMessage");

    public HomePage(WebDriver driver) {
        this.driver = driver;
    }

    public String getWelcomeMessage() {
        return driver.findElement(welcomeMessageLocator).getText();
    }
}

public class TestBase {
    protected WebDriver driver;

    @BeforeClass
    public void setUp() {
        driver = new ChromeDriver();
        driver.manage().window().maximize();
    }

    @AfterClass
    public void tearDown() {
        driver.quit();
    }
}

public class LoginTest extends TestBase {
    private String baseUrl = "http://example.com";
    private String username = "testuser";
    private String password = "testpass";

    @Test
    public void testLogin() {
        driver.get(baseUrl);
        LoginPage loginPage = new LoginPage(driver);
        loginPage.setUsername(username);
        loginPage.setPassword(password);
        loginPage.clickLoginButton();
        HomePage homePage = new HomePage(driver);
        String welcomeMessage = homePage.getWelcomeMessage();
        Assert.assertEquals(welcomeMessage, "Welcome, " + username + "!");
    }
}

这个框架使用了Page Object模式，将页面元素和操作封装在了对应的Page类中，使得测试用例更加清晰易读。同时，使用了TESTng框架来管理测试用例的执行顺序和测试结果的输出。