使用TestNG XML分组运行测试类时出现NullPointerException

我是Selenium新手，尝试通过XML文件运行两个已分组的测试类。但在XML中添加<groups>标签执行smoke组时抛出NullPointerException，直接运行类则正常。

我已尝试在@BeforeMethod中初始化WebDriver，但使用<groups>标签指定分组时，Driver并未完成初始化。

XML文件内容 #

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
<suite name="Annotation running">

    <test name="Annotation Test Runner With Group!" >
        <groups>
            <run>
                <include name="smoke"/>
            </run>
        </groups>
        <classes>
            <class name="DemoPractise.Annotation"/>
            <class name="DemoPractise.annotation2"/>

        </classes>
    </test>

</suite>

错误日志 #

java.lang.NullPointerException
    at DemoPractise.Annotation.test2_BtsListBox(Annotation.java:31)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.testng.internal.invokers.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:139)
    at org.testng.internal.invokers.TestInvoker.invokeMethod(TestInvoker.java:664)
    at org.testng.internal.invokers.TestInvoker.invokeTestMethod(TestInvoker.java:227)
    at org.testng.internal.invokers.MethodRunner.runInSequence(MethodRunner.java:50)
    at org.testng.internal.invokers.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:957)
    at org.testng.internal.invokers.TestInvoker.invokeTestMethods(TestInvoker.java:200)
    at org.testng.internal.invokers.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:148)
    at org.testng.internal.invokers.TestMethodWorker.run(TestMethodWorker.java:128)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.testng.TestRunner.privateRun(TestRunner.java:848)
    at org.testng.TestRunner.run(TestRunner.java:621)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:443)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:437)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:397)
    at org.testng.SuiteRunner.run(SuiteRunner.java:336)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:95)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1280)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1200)
    at org.testng.TestNG.runSuites(TestNG.java:1114)
    at org.testng.TestNG.run(TestNG.java:1082)
    at com.intellij.rt.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:66)
    at com.intellij.rt.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:105)


java.lang.NullPointerException
    at DemoPractise.annotation2.test4_JQueryListBox(annotation2.java:32)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.testng.internal.invokers.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:139)
    at org.testng.internal.invokers.TestInvoker.invokeMethod(TestInvoker.java:664)
    at org.testng.internal.invokers.TestInvoker.invokeTestMethod(TestInvoker.java:227)
    at org.testng.internal.invokers.MethodRunner.runInSequence(MethodRunner.java:50)
    at org.testng.internal.invokers.TestInvoker$MethodInvocationAgent.invoke(TestInvoker.java:957)
    at org.testng.internal.invokers.TestInvoker.invokeTestMethods(TestInvoker.java:200)
    at org.testng.internal.invokers.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:148)
    at org.testng.internal.invokers.TestMethodWorker.run(TestMethodWorker.java:128)
    at java.base/java.util.ArrayList.forEach(ArrayList.java:1541)
    at org.testng.TestRunner.privateRun(TestRunner.java:848)
    at org.testng.TestRunner.run(TestRunner.java:621)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:443)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:437)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:397)
    at org.testng.SuiteRunner.run(SuiteRunner.java:336)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:95)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1280)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1200)
    at org.testng.TestNG.runSuites(TestNG.java:1114)
    at org.testng.TestNG.run(TestNG.java:1082)
    at com.intellij.rt.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:66)
    at com.intellij.rt.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:105)


===============================================
Annotation running
Total tests run: 2, Passes: 0, Failures: 2, Skips: 0
===============================================


Process finished with exit code 0

核心问题是TestNG按分组执行时，仅会触发与测试方法同组的前置方法。如果你的@BeforeMethod未标记smoke分组，分组执行时该方法不会运行，导致WebDriver未初始化，最终抛出空指针异常。

方法一：给@BeforeMethod添加分组标记 #

在测试类中，给初始化WebDriver的@BeforeMethod添加groups属性，确保分组执行时前置方法被调用：

import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;

public class Annotation {
    private WebDriver driver;

    @BeforeMethod(groups = {"smoke"})
    public void setUp() {
        // WebDriver初始化代码
        driver = new ChromeDriver();
        driver.manage().window().maximize();
    }

    @Test(groups = {"smoke"})
    public void test2_BtsListBox() {
        // 此处使用driver执行操作不会空指针
        driver.get("https://example.com");
    }
}

方法二：XML配置强制执行所有前置方法 #

若不想给每个前置方法加分组标记，可在XML的<test>标签中添加方法选择器，强制执行所有前置方法：

<test name="Annotation Test Runner With Group!" preserve-order="true">
    <groups>
        <run>
            <include name="smoke"/>
        </run>
    </groups>
    <method-selectors>
        <method-selector>
            <script language="javascript">
                <![CDATA[
                    return true;
                ]]>
            </script>
        </method-selector>
    </method-selectors>
    <classes>
        <class name="DemoPractise.Annotation"/>
        <class name="DemoPractise.annotation2"/>
    </classes>
</test>

额外检查点 #

• 确认测试方法已标记@Test(groups = {"smoke"})，否则XML分组配置不会选中这些方法
• 检查WebDriver初始化代码是否存在配置错误（如驱动路径问题），不过直接运行类正常的话，此可能性较低

内容的提问来源于stack exchange，提问作者Kaiser