使用POM模式的Selenium测试报错：无法实例化FBLoginTest类

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2026-7-31

Selenium POM测试报错：Cannot instantiate class co.edureka.tests.FBLoginTest 解决方案

使用Selenium页面对象模型（POM）编写测试代码时，出现报错**"Cannot instantiate class co.edureka.tests.FBLoginTest"**，怀疑与重复创建WebDriver实例有关，但未找到解决方法。以下是完整报错信息及相关代码：

相关代码文件

FBLoginPage.java

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.FindBy;
import org.openqa.selenium.support.How;


public class FBLoginPage {
    

    WebDriver driver;
    
    public FBLoginPage(WebDriver driver) {
        this.driver=driver;
        
    
    }
    
    @FindBy(how=How.XPATH, using="/html/body/div[1]/div[1]/div[1]/div/div/div/div[2]/div/div[1]/form/div[1]/div[1]/input")
    public WebElement emailTextBox;
    @FindBy(how=How.XPATH, using="//input[@type='password'][@name='pass']") WebElement passwordTextBox;
    @FindBy(how=How.XPATH, using="//input[@type='submit'][@value='Log In']") WebElement signinButton;
    
    // 设置邮箱
    public void setEmail(String strEmail) {
        emailTextBox.sendKeys(strEmail);
    }
    // 设置密码
    public void setPassword(String strPassword) {
        passwordTextBox.sendKeys(strPassword);
    }
    // 点击登录按钮
    public void clickOnLoginButton() {
        signinButton.click();
    }
}

FBHomePage.java

package co.edureka.pages;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.FindBy;
import org.openqa.selenium.support.How;



public class FBHomePage {
    WebDriver driver;
    
    public FBHomePage(WebDriver driver) {
        this.driver=driver;
    }
    
@FindBy(how=How.XPATH, using="//div[text()='Account Settings']") WebElement profileDropdown;
@FindBy(how=How.LINK_TEXT, using="Log Out") WebElement logoutLink;


// 点击个人资料下拉菜单
public void clickOnProfileDropdown() {
    profileDropdown.click();
}

// 点击退出链接
public void clickOnLogoutLink() {
    logoutLink.click();
}
}

TestBase.java

package co.edureka.tests;

import java.io.IOException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterSuite;
import org.testng.annotations.BeforeSuite;

public class TestBase {
    
    public static WebDriver driver;
    
@BeforeSuite
public void initialize() throws IOException{
    System.setProperty("webdriver.chrome.driver", "C:\\Program Files (x86)\\Drivers\\chromedriver.exe");
    driver = new ChromeDriver();
    WebDriver driver = new ChromeDriver();
    

    
    driver.manage().window().maximize();
    driver.get("https://www.facebook.com");
}

    

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

}

FBLoginTest.java

package co.edureka.tests;

import java.time.Duration;
import org.openqa.selenium.support.PageFactory;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.WebDriverWait;

import org.testng.annotations.Test;
import co.edureka.pages.FBHomePage;
import co.edureka.pages.FBLoginPage;



public class FBLoginTest extends TestBase {
    WebDriverWait wait = new WebDriverWait(driver, Duration.ofSeconds(30));


@Test
public void init() throws Exception{
    //driver.get("https://www.facebook.com");
    FBLoginPage loginpage = PageFactory.initElements(driver, FBLoginPage.class);
    wait.until(ExpectedConditions.titleContains("Facebook"));
    loginpage.setEmail("432547@gmail.com");
    loginpage.setPassword("ashish.bakshi@selenium");
    loginpage.clickOnLoginButton();
    
    FBHomePage homepage = PageFactory.initElements(driver, FBHomePage.class);
    homepage.clickOnProfileDropdown();
    homepage.clickOnLogoutLink();
}
}

报错控制台信息

[RemoteTestNG] detected TestNG version 7.4.0
org.testng.TestNGException: 
Cannot instantiate class co.edureka.tests.FBLoginTest
    at org.testng.internal.ObjectFactoryImpl.newInstance(ObjectFactoryImpl.java:30)
    at org.testng.internal.InstanceCreator.instantiateUsingDefaultConstructor(InstanceCreator.java:193)
    at org.testng.internal.InstanceCreator.createInstanceUsingObjectFactory(InstanceCreator.java:113)
    at org.testng.internal.InstanceCreator.createInstance(InstanceCreator.java:79)
    at org.testng.internal.objects.SimpleObjectDispenser.dispense(SimpleObjectDispenser.java:25)
    at org.testng.internal.objects.GuiceBasedObjectDispenser.dispense(GuiceBasedObjectDispenser.java:30)
    at org.testng.internal.ClassImpl.getDefaultInstance(ClassImpl.java:112)
    at org.testng.internal.ClassImpl.getInstances(ClassImpl.java:165)
    at org.testng.TestClass.getInstances(TestClass.java:122)
    at org.testng.TestClass.initTestClassesAndInstances(TestClass.java:102)
    at org.testng.TestClass.init(TestClass.java:94)
    at org.testng.TestClass.<init>(TestClass.java:59)
    at org.testng.TestRunner.initMethods(TestRunner.java:463)
    at org.testng.TestRunner.init(TestRunner.java:339)
    at org.testng.TestRunner.init(TestRunner.java:292)
    at org.testng.TestRunner.<init>(TestRunner.java:223)
    at org.testng.remote.support.RemoteTestNG6_12$1.newTestRunner(RemoteTestNG6_12.java:33)
    at org.testng.remote.support.RemoteTestNG6_12$DelegatingTestRunnerFactory.newTestRunner(RemoteTestNG6_12.java:66)
    at org.testng.ITestRunnerFactory.newTestRunner(ITestRunnerFactory.java:55)
    at org.testng.SuiteRunner$ProxyTestRunnerFactory.newTestRunner(SuiteRunner.java:659)
    at org.testng.SuiteRunner.init(SuiteRunner.java:173)
    at org.testng.SuiteRunner.<init>(SuiteRunner.java:107)
    at org.testng.TestNG.createSuiteRunner(TestNG.java:1300)
    at org.testng.TestNG.createSuiteRunners(TestNG.java:1276)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1125)
    at org.testng.TestNG.runSuites(TestNG.java:1063)
    at org.testng.TestNG.run(TestNG.java:1031)
    at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:115)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)
Caused by: java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:79)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:499)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:483)
    at org.testng.internal.ObjectFactoryImpl.newInstance(ObjectFactoryImpl.java:23)
    ... 29 more
Caused by: java.lang.IllegalArgumentException: Input must be set
    at org.openqa.selenium.internal.Require.nonNull(Require.java:59)
    at org.openqa.selenium.support.ui.FluentWait.<init>(FluentWait.java:97)
    at org.openqa.selenium.support.ui.WebDriverWait.<init>(WebDriverWait.java:77)
    at org.openqa.selenium.support.ui.WebDriverWait.<init>(WebDriverWait.java:46)
    at co.edureka.tests.FBLoginTest.<init>(FBLoginTest.java:15)
    at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:67)
    ... 32 more

解决建议

从报错栈可以看出，核心问题是**WebDriverWait初始化时driver为null**，同时TestBase存在重复创建WebDriver的问题，具体修复步骤如下：

1. 修复TestBase中重复创建WebDriver的问题

TestBase的initialize方法里重复创建了WebDriver实例，其中WebDriver driver = new ChromeDriver();是局部变量，会覆盖静态变量的引用，导致后续操作混乱。删除该行代码，保留静态driver的初始化：

修改后的TestBase.java：

package co.edureka.tests;

import java.io.IOException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterSuite;
import org.testng.annotations.BeforeSuite;

public class TestBase {
    
    public static WebDriver driver;
    
    @BeforeSuite
    public void initialize() throws IOException{
        System.setProperty("webdriver.chrome.driver", "C:\\Program Files (x86)\\Drivers\\chromedriver.exe");
        // 移除重复创建的局部driver实例
        driver = new ChromeDriver();
        
        driver.manage().window().maximize();
        driver.get("https://www.facebook.com");
    }
    
    @AfterSuite
    public void TeardownTest()
    {
        TestBase.driver.quit();
    }
}

2. 调整WebDriverWait的初始化时机

FBLoginTest中WebDriverWait作为成员变量，会在类实例化时初始化，但此时TestBase的@BeforeSuite还未执行，driver还是null，导致报错。需要将WebDriverWait的初始化延迟到driver创建完成后，比如用@BeforeMethod注解：

修改后的FBLoginTest.java：

package co.edureka.tests;

import java.time.Duration;
import org.openqa.selenium.support.PageFactory;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.WebDriverWait;

import org.testng.annotations.BeforeMethod;
import org.testng.annotations.Test;
import co.edureka.pages.FBHomePage;
import co.edureka.pages.FBLoginPage;

public class FBLoginTest extends TestBase {
    private WebDriverWait wait;

    @BeforeMethod
    public void setupWait() {
        // 在BeforeMethod中初始化wait，此时driver已被BeforeSuite初始化完成
        wait = new WebDriverWait(driver, Duration.ofSeconds(30));
    }

    @Test
    public void init() throws Exception{
        FBLoginPage loginpage = PageFactory.initElements(driver, FBLoginPage.class);
        wait.until(ExpectedConditions.titleContains("Facebook"));
        loginpage.setEmail("432547@gmail.com");
        loginpage.setPassword("ashish.bakshi@selenium");
        loginpage.clickOnLoginButton();
        
        FBHomePage homepage = PageFactory.initElements(driver, FBHomePage.class);
        homepage.clickOnProfileDropdown();
        homepage.clickOnLogoutLink();
    }
}

3. 优化POM页面对象（可选）

页面对象类的构造函数中建议加入PageFactory.initElements，将元素初始化逻辑封装在页面对象内部，符合POM规范：

修改后的FBLoginPage.java：

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.FindBy;
import org.openqa.selenium.support.How;
import org.openqa.selenium.support.PageFactory;

public class FBLoginPage {
    
    WebDriver driver;
    
    public FBLoginPage(WebDriver driver) {
        this.driver = driver;
        // 在构造函数中初始化页面元素
        PageFactory.initElements(driver, this);
    }
    
    @FindBy(how=How.XPATH, using="/html/body/div[1]/div[1]/div[1]/div/div/div/div[2]/div/div[1]/form/div[1]/div[1]/input")
    public WebElement emailTextBox;
    @FindBy(how=How.XPATH, using="//input[@type='password'][@name='pass']") WebElement passwordTextBox;
    @FindBy(how=How.XPATH, using="//input[@type='submit'][@value='Log In']") WebElement signinButton;
    
    public void setEmail(String strEmail) {
        emailTextBox.sendKeys(strEmail);
    }
    public void setPassword(String strPassword) {
        passwordTextBox.sendKeys(strPassword);
    }
    public void clickOnLoginButton() {
        signinButton.click();
    }
}

对应的FBHomePage.java也做同样修改，测试类中初始化页面对象时就可以简化为：

FBLoginPage loginpage = new FBLoginPage(driver);
FBHomePage homepage = new FBHomePage(driver);

内容的提问来源于stack exchange，提问作者Owen Bonham

使用POM模式的Selenium测试报错：无法实例化FBLoginTest类

相关代码文件 #

FBLoginPage.java #

FBHomePage.java #

TestBase.java #

FBLoginTest.java #

报错控制台信息 #

解决建议 #

1. 修复TestBase中重复创建WebDriver的问题 #

2. 调整WebDriverWait的初始化时机 #

3. 优化POM页面对象（可选） #