我正在用TestNG编写一个简单的Selenium代码。我已经在基类中初始化了驱动程序，页面类和测试类都在扩展基类，但是驱动程序没有在页面类中继承。但是，相同的驱动程序在测试类中继承。有人能解释一下为什么会发生这种情况吗？编辑：从页面类中删除了WebDriver驱动程序，但它给出了相同的错误：java.lang.NullPointerException：无法调用“org.openqa.selenium.WebDriver.get（字符串）”，因为“此.driver”为空

基类

public class BaseClass {
protected WebDriver driver;
protected String username;
protected String password;
protected String browserName;
protected String url;

@BeforeSuite
public void setUp() throws IOException, InterruptedException {
    username = "admin";
    password = "admin";
    browserName = "chrome";
    url = "https://practice-cybertekschool.herokuapp.com/";

    // get the driver setp and type and the browser
    if (browserName.equalsIgnoreCase("Chrome")) {
        WebDriverManager.chromedriver().setup();
        driver = new ChromeDriver();
    } else if (browserName.equalsIgnoreCase("FireFox")) {
        WebDriverManager.firefoxdriver().setup();
        driver = new FirefoxDriver();
    } else if (browserName.equalsIgnoreCase("Edge")) {
        WebDriverManager.edgedriver().setup();
        driver = new EdgeDriver();
    }

    driver.manage().deleteAllCookies();
    driver.manage().window().maximize();

    driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(30));
    driver.manage().timeouts().pageLoadTimeout(Duration.ofSeconds(30));
    driver.get(url);

}

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

}

页面类

public class BasicAuthPages extends BaseClass {

    By congratulationMessage = By.xpath("//p[contains(text(),'Congratulations')]");
    

// for authentication
public boolean authentication() {

    driver.get("https://"+username+":"+password+"@practice-cybertekschool.herokuapp.com/basic_auth");
    return authenticationMessage();
}

// to get authentication message
private boolean authenticationMessage() {
    String message = driver.findElement(congratulationMessage).getText();
    //System.out.println(message);
    if (message.equals("Congratulations! You must have the proper credentials.")) {
        return true;
    }

    else {
        return false;
    }
}

}

测试类别

public class Tests extends BaseClass {
    BasicAuthPages basicAuthPages;
    

@Test
public void authTest() {
    basicAuthPages = new BasicAuthPages();
    Boolean success = basicAuthPages.authentication();
    // System.out.println(username+" :"+password);
    Assert.assertTrue(success);
}
}

在运行这个函数时，它会给出java.lang.NullPointerException异常：无法调用“org.openqa.selenium.WebDriver.get（String）”，因为“this.driver”是空异常。但是，驱动程序在Test类中初始化，如果我进行以下更改，它将运行。

基类

public class BaseClass {
protected WebDriver driver;
protected String username;
protected String password;
protected String browserName;
protected String url;

@BeforeSuite
public void setUp() throws IOException, InterruptedException {
    username = "admin";
    password = "admin";
    browserName = "chrome";
    url = "https://practice-cybertekschool.herokuapp.com/";

    // get the driver setp and type and the browser
    if (browserName.equalsIgnoreCase("Chrome")) {
        WebDriverManager.chromedriver().setup();
        driver = new ChromeDriver();
    } else if (browserName.equalsIgnoreCase("FireFox")) {
        WebDriverManager.firefoxdriver().setup();
        driver = new FirefoxDriver();
    } else if (browserName.equalsIgnoreCase("Edge")) {
        WebDriverManager.edgedriver().setup();
        driver = new EdgeDriver();
    }

    driver.manage().deleteAllCookies();
    driver.manage().window().maximize();

    driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(30));
    driver.manage().timeouts().pageLoadTimeout(Duration.ofSeconds(30));
    driver.get(url);

}

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

}

页面类

public class BasicAuthPages extends BaseClass {
WebDriver driver;
By congratulationMessage = By.xpath("//p[contains(text(),'Congratulations')]");

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

// for authentication
public boolean authentication(String username, String password) {
    driver.get("https://"+username+":"+password+"@practice-cybertekschool.herokuapp.com/basic_auth");
    return authenticationMessage();
}

// to get authentication message
private boolean authenticationMessage() {
    String message = driver.findElement(congratulationMessage).getText();
    //System.out.println(message);
    if (message.equals("Congratulations! You must have the proper credentials.")) {
        return true;
    }

    else {
        return false;
    }
}

}

测试类别

public class Tests extends BaseClass {
BasicAuthPages basicAuthPages;
CheckBoxPages checkBoxPages;

@Test
public void authTest() {
    basicAuthPages = new BasicAuthPages(driver);
    Boolean success = basicAuthPages.authentication(username, password);
    // System.out.println(username+" :"+password);
    Assert.assertTrue(success);
}
}

请有人解释一下为什么驱动程序在第一种情况下没有被继承？驱动程序在第二种情况下被继承，在测试类中被继承，为什么不在页面类的第一种情况下被继承？提前感谢