所以我想测试一下这个链接的名字部分(https://softwaretestinggn8fe.herokuapp.com/)在java中使用selenium来显示错误消息“firstname只能包含字符”。当我在网站的firstname部分键入“545”时，将显示该消息。但是我的测试失败了，这是我得到的错误：

org.openqa.selenium.NoSuchElementException: no such element: Unable to locate element: {"method":"css selector","selector":"*[name='submit']"}
  (Session info: chrome=86.0.4240.198)

有人知道如何解决这个问题吗？

import org.testng.AssertJUnit;
    import org.openqa.selenium.By;
    import org.openqa.selenium.WebDriver;
    import org.openqa.selenium.WebElement;
    import org.openqa.selenium.chrome.ChromeDriver;
    import org.testng.Assert;
    import org.testng.annotations.Test;

    public class WebTesting {

        @Test
        public void test1() {

            System.setProperty("webdriver.chrome.driver", "C:/Users/mtecl/Desktop/Drivers/chromedriver.exe");    // configure path to the driver

            WebDriver driver = new ChromeDriver();

            driver.get("https://softwaretestinggn8fe.herokuapp.com/");

            //Username
            WebElement testUsername = driver.findElement(By.id("firstname")); //id: first name

            testUsername.sendKeys("545");

            //Button
            driver.findElement(By.name("submit")).click();

            String expected = "First Name can only contain characters.";
            String actual = driver.findElement(By.xpath("html/body/div/main/div[2]/form/div[1]/span")).getText();

            Assert.assertEquals(expected, actual);

        }
    }