使用 TestNG 在 Selenium WebDriver 中获取空指针异常

Question

我是 Selenium 的新手，当 运行 下面的脚本出现空指针异常时，一旦调用的站点加载，测试就会停止 运行。我无法理解异常的原因。

代码如下：

package TestNGPackage;

import java.util.concurrent.TimeUnit;

import org.openqa.selenium.support.ui.*;
import org.openqa.selenium.firefox.*;
import org.openqa.selenium.*;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.BeforeMethod;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;
import org.testng.annotations.BeforeTest;

public class ParameterizationTest {
WebDriver driver;
  @Test(dataProvider="getdata")
  public void Login(String Username, String Password) 
  {
    //WebDriverWait wait= new WebDriverWait(driver,60);
    //WebElement username= wait.until(ExpectedConditions.visibilityOfElementLocated(By.id("username")));
    WebElement username=driver.findElement(By.id("username"));
        WebElement password= driver.findElement(By.id("password"));
        username.sendKeys(Username);
        password.sendKeys(Password);
        WebElement SignIn= driver.findElement(By.tagName("button"));
        String text = SignIn.getText();
        if (text.equalsIgnoreCase("sign in")) {
            // sign in btn
            SignIn.submit();
        }
  }

  @DataProvider(name="getdata")
  public Object[][] testgetdata()
  {
      Object[][] data = new Object[3][2];
      //row1
      data[0][0]="ho@abc.com";
      data[0][1]="welcome23";
      //row2
      data[1][0]="ho@baskin.com";
      data[1][1]="welcome23";
      //row3
      data[2][0]="ho@nike.com";
      data[2][1]="welcome23";

      return data;
  }

  @BeforeMethod
  public void beforeTest() {
      WebDriver driver = new FirefoxDriver();

      driver.get("http://52.25.202.63/illweb/");
    //  driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);

  }

  @AfterMethod
  public void AfterTest() {
      //driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);
        WebElement logout = driver.findElement(By.linkText("Logout"));
        logout.click();
        //driver.manage().timeouts().implicitlyWait(30, TimeUnit.SECONDS);
        driver.close();

  }
}

我收到以下错误：

[TestNG] Running: C:\Users\Ronit\AppData\Local\Temp\testng-eclipse--473949223\testng-customsuite.xml [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\Default suite\Default test.xml [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\Default suite exists: true FAILED CONFIGURATION: @AfterMethod AfterTest java.lang.NullPointerException at TestNGPackage.ParameterizationTest.AfterTest(ParameterizationTest.java:60) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:100) at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:515) at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:216) at org.testng.internal.Invoker.invokeMethod(Invoker.java:712) at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:811) at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1129) at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:129) at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:112) at org.testng.TestRunner.privateRun(TestRunner.java:746) at org.testng.TestRunner.run(TestRunner.java:600) at org.testng.SuiteRunner.runTest(SuiteRunner.java:366) at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:361) at org.testng.SuiteRunner.privateRun(SuiteRunner.java:319) at org.testng.SuiteRunner.run(SuiteRunner.java:268) at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52) at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86) at org.testng.TestNG.runSuitesSequentially(TestNG.java:1264) at org.testng.TestNG.runSuitesLocally(TestNG.java:1189) at org.testng.TestNG.runSuites(TestNG.java:1104) at org.testng.TestNG.run(TestNG.java:1076) at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:126) at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:152) at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:57) SKIPPED CONFIGURATION: @BeforeMethod beforeTest SKIPPED CONFIGURATION: @AfterMethod AfterTest SKIPPED CONFIGURATION: @BeforeMethod beforeTest SKIPPED CONFIGURATION: @AfterMethod AfterTest FAILED: Login("manjeet@wtechspaces.in", "p@ssw0rd") java.lang.NullPointerException at TestNGPackage.ParameterizationTest.Login(ParameterizationTest.java:20) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:100) at org.testng.internal.Invoker.invokeMethod(Invoker.java:646) at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:811) at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1129) at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:129) at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:112) at org.testng.TestRunner.privateRun(TestRunner.java:746) at org.testng.TestRunner.run(TestRunner.java:600) at org.testng.SuiteRunner.runTest(SuiteRunner.java:366) at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:361) at org.testng.SuiteRunner.privateRun(SuiteRunner.java:319) at org.testng.SuiteRunner.run(SuiteRunner.java:268) at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52) at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86) at org.testng.TestNG.runSuitesSequentially(TestNG.java:1264) at org.testng.TestNG.runSuitesLocally(TestNG.java:1189) at org.testng.TestNG.runSuites(TestNG.java:1104) at org.testng.TestNG.run(TestNG.java:1076) at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:126) at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:152) at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:57) SKIPPED: Login("ho@baskin.com", "welcome123") SKIPPED: Login("ho@nike.com", "welcome123") =============================================== Default test Tests run: 3, Failures: 1, Skips: 2 Configuration Failures: 1, Skips: 4 =============================================== =============================================== Default suite Total tests run: 3, Failures: 1, Skips: 2 Configuration Failures: 1, Skips: 4 =============================================== [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\testng-failed.xml [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\Default suite\testng-failed.xml [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\Default suite exists: true [TestNG] Time taken by [FailedReporter passed=0 failed=0 skipped=0]: 36 ms [TestNG] Time taken by org.testng.reporters.XMLReporter@5594a1b5: 30 ms [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\junitreports\TEST-TestNGPackage.ParameterizationTest.xml [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\junitreports exists: true [TestNG] Time taken by org.testng.reporters.JUnitReportReporter@3f3afe78: 15 ms [TestNG] Time taken by org.testng.reporters.jq.Main@1cd072a9: 228 ms [TestNG] Time taken by org.testng.reporters.EmailableReporter2@34ce8af7: 8 ms [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\toc.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\Default test.properties [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\index.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\main.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\groups.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\classes.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\reporter-output.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\methods-not-run.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite\testng.xml.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\Default suite exists: true [Utils] Attempting to create C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old\index.html [Utils] Directory C:\Users\Ronit\workspace\FirstTestNGProject\test-output\old exists: true [TestNG] Time taken by org.testng.reporters.SuiteHTMLReporter@6b71769e: 58 ms

请帮我解决我做错的地方，在此先感谢！

Answer 1

您发现 NullPointerException 导致驱动程序在此之前未初始化。您尝试在 beforeTest() 方法中初始化 WebDriver 实例，但它是本地的。要解决此问题，只需在 beforeTest() 方法中初始化该 WebDriver 而无需重新声明为：

driver = new FirefoxDriver();

不是

WebDriver driver = new FirefoxDriver();

第二个NullPointerExpception也是同样的原因造成的