在 TestNG 中运行多个类

我正在尝试自动化一个场景，其中我想登录一次应用程序 &然后无需重新登录即可进行操作.

I am trying to automate a scenario wherein, I want to Login once into the application & then do manipulations without having to re-login again.

考虑到这一点，我在特定类的@BeforeSuite 方法中有用于登录应用程序的代码.

Consider that, I have the code to login into the application in the @BeforeSuite method in a specific class.

public class TestNGClass1 {

    public static WebDriver driver;

    @BeforeSuite
    public static void setUp(){
        System.setProperty("webdriver.chrome.driver", "D://Softwares//chromedriver.exe");
        driver = new ChromeDriver(); 
        //driver = new FirefoxDriver();
        driver.manage().window().maximize();
        driver.get("https://www.myfitnesspal.com");
    }

    @AfterSuite
    public static void close(){
        driver.close();
    }
}

我在 TestNGClass2 中有我的 @test 方法，它基本上试图点击一些登录按钮.

I have my @test method in TestNGClass2 which basically tries to click on some login buttons.

public class TestNGClass2 extends TestNGClass1 {

    public static WebDriver driver;

    @Test
    public static void login(){
        System.out.println("Entering the searchQuery Box");
        WebElement signUpWithEmailBtn = driver.findElement(By.xpath(".//*[@id='join']/a[2]"));
        System.out.println("srchTxtBox Box");
        signUpWithEmailBtn.click();
    }   
}

我有另一个类 TestNGClass3，它有另一个 @Test 方法，需要在 TestNGClass2 完成后运行.

I have another class TestNGClass3 which has another @Test method which needs to be run after TestNGClass2 is completed.

public class TestNGClass3 extends TestNGClass1{

public static WebDriver driver;

    @Test
    public static void signIn(){
        WebElement emailAddress = driver.findElement(By.id("user_email"));
        emailAddress.clear();
        emailAddress.sendKeys("asdsa@gmail.com");
        WebElement password = driver.findElement(By.id("user_password"));
        password.clear();
        password.sendKeys("sdass");

        WebElement continueBtn = driver.findElement(By.id("submit"));
        continueBtn.click();
    }
}

testng.xml 文件如下:

testng.xml file is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite name="Suite">
    <test name="Regression Test">
        <classes>
            <class name="com.test.TestNGClass2" />
            <class name="com.test.TestNGClass3" />
        </classes>
    </test> <!-- Test -->
</suite> <!-- Suite -->

我的方法是否正确，因为当代码到达 TestNGClass2 的登录"方法时出现空指针"异常?

Is my approach right, since I'm getting "Null Pointer" exception when the code reaches the 'login' method of TestNGClass2 ?