java.lang.NullPointer异常（TestNG）

我有一个“BaseTest”类，其中包含与web驱动程序相关的代码以及所有BeforeTest和AfterTest方法。我在'Login'文件和'skillsaquisition'文件中扩展了这个方法，但是只有登录文件运行良好，我在第二个文件中得到了NullPointer异常。我不知道我做错了什么

我对Selenium和testng是新手，因此非常感谢您的帮助

BaseTest.java

package Students;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.NoAlertPresentException;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeTest;

public class BaseTest {

    String driverPath = "my_path_to_chromedriver";
    public String baseUrl = "some_url";

    public WebDriver driver ; 
    public String expected = null;
    public String actual = null;
    private boolean acceptNextAlert;
    
    @BeforeTest
    public void launchBrowser() {
        System.out.println("launching Chrome browser"); 
        System.setProperty("webdriver.chrome.driver", driverPath);
        driver= new ChromeDriver();
        driver.manage().window().maximize();
        driver.get(baseUrl);
    }
    
    @AfterTest
    public void terminateBrowser(){
        driver.close();
    }
    
    private boolean isElementPresent(By by) {
        try {
          driver.findElement(by);
          return true;
        } catch (NoSuchElementException e) {
          return false;
        }
      }

      private boolean isAlertPresent() {
        try {
          driver.switchTo().alert();
          return true;
        } catch (NoAlertPresentException e) {
          return false;
        }
      }

      private String closeAlertAndGetItsText() {
        try {
          Alert alert = driver.switchTo().alert();
          String alertText = alert.getText();
          if (acceptNextAlert) {
            alert.accept();
          } else {
            alert.dismiss();
          }
          return alertText;
        } finally {
          acceptNextAlert = true;
        }
      }

}

package Students;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.Keys;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.Assert;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;

public class Login extends BaseTest{
    
        @Test(priority = 0)
        public void login() throws InterruptedException{
            driver.findElement(By.id("Username")).clear();
            driver.findElement(By.id("Username")).sendKeys("my_username");
            driver.findElement(By.id("Password")).clear();
            driver.findElement(By.id("Password")).sendKeys("my_password");
            driver.findElement(By.id("Password")).sendKeys(Keys.RETURN);
            expected = "Expected Text";
            actual = driver.getTitle();
            Assert.assertEquals(actual, expected);  
    }
}

package Students;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.Keys;
import org.openqa.selenium.NoAlertPresentException;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.testng.Assert;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.Select;
import org.openqa.selenium.support.ui.WebDriverWait;

@Test
public class SkillsAcquisition extends BaseTest{

        @Test(priority = 1)
        public void addSkills() throws InterruptedException {
            System.out.println("Test reached Second file");
            WebDriverWait d = new WebDriverWait(driver, 20);            
d.until(ExpectedConditions.visibilityOfAllElementsLocatedBy(By.id("skillAquistionTab")));
            driver.findElement(By.id("skillAquistionTab")).click();
            Thread.sleep(3000);
            d.until(ExpectedConditions.visibilityOfAllElementsLocatedBy(By.xpath("//a[@class='add']")));
            Thread.sleep(3000);
            driver.findElement(By.xpath("//a[@class='add']")).click();      
            System.out.println("Added");
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).click();
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).clear();
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).sendKeys("Skill1");
            driver.findElement(By.id("page-wrapper-1")).click();
            Thread.sleep(2000);
            driver.findElement(By.linkText("Skill1")).click();
            Thread.sleep(3000);
            driver.findElement(By.id("addProgramButton")).click();
            Thread.sleep(2000);
            driver.findElement(By.id("ProgramName")).clear();
            driver.findElement(By.id("ProgramName")).sendKeys("Program1");
            driver.findElement(By.id("SaveNewProgram")).click();
            Thread.sleep(2000);
            String Newprogramname = driver.findElement(By.linkText("Program1")).getText();
            String createdprogramName = "Program1";
            Assert.assertEquals(Newprogramname,createdprogramName);
            System.out.println("Program created sucessfully");
        }   
    }

Login.java

package Students;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.NoAlertPresentException;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeTest;

public class BaseTest {

    String driverPath = "my_path_to_chromedriver";
    public String baseUrl = "some_url";

    public WebDriver driver ; 
    public String expected = null;
    public String actual = null;
    private boolean acceptNextAlert;
    
    @BeforeTest
    public void launchBrowser() {
        System.out.println("launching Chrome browser"); 
        System.setProperty("webdriver.chrome.driver", driverPath);
        driver= new ChromeDriver();
        driver.manage().window().maximize();
        driver.get(baseUrl);
    }
    
    @AfterTest
    public void terminateBrowser(){
        driver.close();
    }
    
    private boolean isElementPresent(By by) {
        try {
          driver.findElement(by);
          return true;
        } catch (NoSuchElementException e) {
          return false;
        }
      }

      private boolean isAlertPresent() {
        try {
          driver.switchTo().alert();
          return true;
        } catch (NoAlertPresentException e) {
          return false;
        }
      }

      private String closeAlertAndGetItsText() {
        try {
          Alert alert = driver.switchTo().alert();
          String alertText = alert.getText();
          if (acceptNextAlert) {
            alert.accept();
          } else {
            alert.dismiss();
          }
          return alertText;
        } finally {
          acceptNextAlert = true;
        }
      }

}

package Students;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.Keys;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.Assert;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;

public class Login extends BaseTest{
    
        @Test(priority = 0)
        public void login() throws InterruptedException{
            driver.findElement(By.id("Username")).clear();
            driver.findElement(By.id("Username")).sendKeys("my_username");
            driver.findElement(By.id("Password")).clear();
            driver.findElement(By.id("Password")).sendKeys("my_password");
            driver.findElement(By.id("Password")).sendKeys(Keys.RETURN);
            expected = "Expected Text";
            actual = driver.getTitle();
            Assert.assertEquals(actual, expected);  
    }
}

package Students;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.Keys;
import org.openqa.selenium.NoAlertPresentException;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.testng.Assert;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.Select;
import org.openqa.selenium.support.ui.WebDriverWait;

@Test
public class SkillsAcquisition extends BaseTest{

        @Test(priority = 1)
        public void addSkills() throws InterruptedException {
            System.out.println("Test reached Second file");
            WebDriverWait d = new WebDriverWait(driver, 20);            
d.until(ExpectedConditions.visibilityOfAllElementsLocatedBy(By.id("skillAquistionTab")));
            driver.findElement(By.id("skillAquistionTab")).click();
            Thread.sleep(3000);
            d.until(ExpectedConditions.visibilityOfAllElementsLocatedBy(By.xpath("//a[@class='add']")));
            Thread.sleep(3000);
            driver.findElement(By.xpath("//a[@class='add']")).click();      
            System.out.println("Added");
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).click();
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).clear();
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).sendKeys("Skill1");
            driver.findElement(By.id("page-wrapper-1")).click();
            Thread.sleep(2000);
            driver.findElement(By.linkText("Skill1")).click();
            Thread.sleep(3000);
            driver.findElement(By.id("addProgramButton")).click();
            Thread.sleep(2000);
            driver.findElement(By.id("ProgramName")).clear();
            driver.findElement(By.id("ProgramName")).sendKeys("Program1");
            driver.findElement(By.id("SaveNewProgram")).click();
            Thread.sleep(2000);
            String Newprogramname = driver.findElement(By.linkText("Program1")).getText();
            String createdprogramName = "Program1";
            Assert.assertEquals(Newprogramname,createdprogramName);
            System.out.println("Program created sucessfully");
        }   
    }

skillsaquisition.java

package Students;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.NoAlertPresentException;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeTest;

public class BaseTest {

    String driverPath = "my_path_to_chromedriver";
    public String baseUrl = "some_url";

    public WebDriver driver ; 
    public String expected = null;
    public String actual = null;
    private boolean acceptNextAlert;
    
    @BeforeTest
    public void launchBrowser() {
        System.out.println("launching Chrome browser"); 
        System.setProperty("webdriver.chrome.driver", driverPath);
        driver= new ChromeDriver();
        driver.manage().window().maximize();
        driver.get(baseUrl);
    }
    
    @AfterTest
    public void terminateBrowser(){
        driver.close();
    }
    
    private boolean isElementPresent(By by) {
        try {
          driver.findElement(by);
          return true;
        } catch (NoSuchElementException e) {
          return false;
        }
      }

      private boolean isAlertPresent() {
        try {
          driver.switchTo().alert();
          return true;
        } catch (NoAlertPresentException e) {
          return false;
        }
      }

      private String closeAlertAndGetItsText() {
        try {
          Alert alert = driver.switchTo().alert();
          String alertText = alert.getText();
          if (acceptNextAlert) {
            alert.accept();
          } else {
            alert.dismiss();
          }
          return alertText;
        } finally {
          acceptNextAlert = true;
        }
      }

}

package Students;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.Keys;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.Assert;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;

public class Login extends BaseTest{
    
        @Test(priority = 0)
        public void login() throws InterruptedException{
            driver.findElement(By.id("Username")).clear();
            driver.findElement(By.id("Username")).sendKeys("my_username");
            driver.findElement(By.id("Password")).clear();
            driver.findElement(By.id("Password")).sendKeys("my_password");
            driver.findElement(By.id("Password")).sendKeys(Keys.RETURN);
            expected = "Expected Text";
            actual = driver.getTitle();
            Assert.assertEquals(actual, expected);  
    }
}

package Students;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import org.openqa.selenium.Alert;
import org.openqa.selenium.By;
import org.openqa.selenium.Keys;
import org.openqa.selenium.NoAlertPresentException;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.testng.Assert;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.BeforeTest;
import org.testng.annotations.Test;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.Select;
import org.openqa.selenium.support.ui.WebDriverWait;

@Test
public class SkillsAcquisition extends BaseTest{

        @Test(priority = 1)
        public void addSkills() throws InterruptedException {
            System.out.println("Test reached Second file");
            WebDriverWait d = new WebDriverWait(driver, 20);            
d.until(ExpectedConditions.visibilityOfAllElementsLocatedBy(By.id("skillAquistionTab")));
            driver.findElement(By.id("skillAquistionTab")).click();
            Thread.sleep(3000);
            d.until(ExpectedConditions.visibilityOfAllElementsLocatedBy(By.xpath("//a[@class='add']")));
            Thread.sleep(3000);
            driver.findElement(By.xpath("//a[@class='add']")).click();      
            System.out.println("Added");
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).click();
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).clear();
            driver.findElement(By.xpath("(//input[@type='text'])[2]")).sendKeys("Skill1");
            driver.findElement(By.id("page-wrapper-1")).click();
            Thread.sleep(2000);
            driver.findElement(By.linkText("Skill1")).click();
            Thread.sleep(3000);
            driver.findElement(By.id("addProgramButton")).click();
            Thread.sleep(2000);
            driver.findElement(By.id("ProgramName")).clear();
            driver.findElement(By.id("ProgramName")).sendKeys("Program1");
            driver.findElement(By.id("SaveNewProgram")).click();
            Thread.sleep(2000);
            String Newprogramname = driver.findElement(By.linkText("Program1")).getText();
            String createdprogramName = "Program1";
            Assert.assertEquals(Newprogramname,createdprogramName);
            System.out.println("Program created sucessfully");
        }   
    }

Testng.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd">
<suite name="Suite">
  <test thread-count="5" name="Test">
    <classes>
      <class name="Students.Login"/>
      <class name="Students.SkillsAcquisition"/>
    </classes>
  </test> 
</suite>

错误的屏幕截图。

---

您需要将

@BeforeTest

更改为

@beforethod

。在对

testng.xml

中的

test

标记执行一次测试之前。这就是为什么您的第一个测试通过了，但第二个测试失败了

另一个选项（仅供参考，但我相信这不是您需要的）是将

testng.xml

更改为：

因为在这里，每个测试类都有自己的

test

标记，所以测试将通过。

---

因为这里您有自己的

test

标记用于每个测试类别

，所以您的驱动程序看起来是空的。从计算技能请求的行数（第33行）来看，这两行中的一行似乎有一个例外`WebDriverWait d=new WebDriverWait（driver，20）；d、 直到（被（By.id（“skillaquisitiontab”））拒绝的所有人员的预期条件、可视性）`是的，

driver

为空，堆栈跟踪指向

WebDriverWait

的构造函数。它不应该从BaseTest.java类中提取驱动程序属性吗？如果没有，请协助我如何解决此错误。我将驱动程序属性添加到此文件中，但它仍然会出错并显示相同的错误消息@SmutjeQuick解决方案-在您的基础上为

getDriver（）

创建一个方法，该方法的作用是：

返回驱动程序-然后，不要直接调用驱动程序，而是调用getDriver。可能还有其他的方法，但由于代码行太多，这很困难。为了获得定制答案的最佳机会，我建议您遵循以下指南：谢谢@RichEdwards的建议。我添加了返回驱动程序的返回类型方法，但它似乎没有起到作用。谢谢@Alexey R.的建议。我尝试了这两种方法，我确实看到web驱动程序按预期工作，但它会为两种方法中的每个测试启动一个新的浏览器。例如，它启动一个浏览器，运行登录测试，然后再次启动另一个浏览器以运行第二个文件。由于第二个文件与登录无关，所以测试只会出错。当然，您需要应用一些设计技巧使代码保持一致。TestNg本身没有给出答案，因为它现在没有任何关于测试逻辑的内容。您可以将一些特定的
@beforethod
添加到负责日志的非登录类中。