出现异常：
Exception in thread "main" org.openqa.selenium.WebDriverException: Cannot find firefox binary in PATH. Make sure firefox is installed. OS appears to be: XP
Build info: version: '2.16.1', revision: '15405', time: '2012-01-05 12:30:12'
具体原因是无法找到firefox浏览器
解决办法：
1.firefox卸载，重新安装到默认路径
2.不卸载，
我们只要在WebDriver driver = new FirefoxDriver(); 前面指定我们浏览器的具体信息即可：
System.setProperty("webdriver.firefox.bin","D:\\Program Files (x86)\\Mozilla Firefox\\firefox.exe"); （这个斜杠要打两个，作为转义字符）
WebDriver driver = new FirefoxDriver();