在使用testng运行硒代码时获得NullPointerException错误消息

Question

package utils;
import org.openqa.selenium.Point;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterTest;
import org.testng.annotations.BeforeTest;
import java.util.concurrent.TimeUnit;
public class BrowserUtils {
    public WebDriver driver = null;
    @BeforeTest
    public void setUp(){
        System.setProperty("webdriver.chrome.driver","C:\Users\sdad\Downloads\Softwares\BrowserDrivers\chromedriver.exe");
        driver = new ChromeDriver();
        driver.manage().deleteAllCookies();
        driver.manage().window().setPosition(new Point(0, 0));
        driver.manage().window().maximize();
        driver.manage().timeouts().implicitlyWait(60, TimeUnit.SECONDS);
        driver.manage().timeouts().pageLoadTimeout(60, TimeUnit.SECONDS);
    }
    @AfterTest
    public void tearDown(){
        driver.close();
        driver.quit();
    }
}

package parallel_3;
import org.testng.Assert;
import org.testng.annotations.Test;
import parallel_2.Headers;
import parallel_2.Images;
import parallel_2.Styles;
import utils.BrowserUtils;
public class Test_01 extends BrowserUtils {
    Headers headers;
    Images images;
    Styles styles;
    private final String HEADER_FILE_PATH ="C:\Users\sdad\Downloads\Projects\Demo-Website\Headers.html",
            IMAGES_FILE_PATH ="C:\Users\sdad\Downloads\Projects\Demo-Website\Images.html";
    @Test
    public void test(){
        driver.get(HEADER_FILE_PATH);
        headers = new Headers(driver);
        Assert.assertEquals(driver.getTitle(), "Headers");
        Assert.assertEquals(headers.header4.getText(), "This is Header 4");
        headers.images_link.click();
        images = new Images(driver);
        Assert.assertEquals(driver.getTitle(), "Images");
        Assert.assertEquals(images.header2.getText(), "Image with width and height");
        images.styles_link.click();
        styles = new Styles(driver);
        Assert.assertEquals(driver.getTitle(), "Page Styles");
        Assert.assertEquals(styles.paragraph.getText(), "This is a paragraph");
        styles.images_link.click();
    }
}

package parallel_3;
import org.testng.Assert;
import org.testng.annotations.Test;
import parallel_2.Headers;
import parallel_2.Images;
import parallel_2.Styles;
import utils.BrowserUtils;
public class Test_02 extends BrowserUtils {
    Headers headers;
    Images images;
    Styles styles;
    private final String HEADER_FILE_PATH ="C:\Users\sdad\Downloads\Projects\Demo-Website\Headers.html",
            IMAGES_FILE_PATH ="C:\Users\sdad\Downloads\Projects\Demo-Website\Images.html";
    @Test
    public void test(){
        driver.get(IMAGES_FILE_PATH);
        images = new Images(driver);
        Assert.assertEquals(driver.getTitle(), "Images");
        Assert.assertEquals(images.header2.getText(), "Image with width and height");
        images.styles_link.click();
        styles = new Styles(driver);
        Assert.assertEquals(driver.getTitle(), "Page Styles");
        Assert.assertEquals(styles.paragraph.getText(), "This is a paragraph");
        styles.images_link.click();
        headers = new Headers(driver);
        Assert.assertEquals(driver.getTitle(), "Headers");
        Assert.assertEquals(headers.header4.getText(), "This is Header 4");
        headers.images_link.click();
    }
}

错误信息

java.lang.NullPointerException
    at parallel_3.Test_01.test(Test_01.java:20)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:124)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:583)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:719)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:989)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)

Answer 1

@BeforeTest不会在所有@Test运行，只在第一个之前运行，因此driver永远不会初始化。来自测试文档

@BeforeTest: The annotated method will be run before any test method belonging to the classes inside the <test> tag is run.

您可以使用@BeforeMethod注释

@BeforeMethod: The annotated method will be run before each test method.

@AfterTest和@AfterMethod也是如此。