运行 phpunit 时找不到致命错误“文件/迭代器/自动加载.php”

当我尝试在phpunit中运行testclass时，我得到了这个错误。

C:\xampp\htdocs\unittest>phpunit UnitTest usertest.php
PHP Warning:  require_once(File/Iterator/Autoload.php): failed to open stream No such file or directory in C:\xampp\php\pear\PHPUnit\Autoload.php on line 45
PHP Stack trace:
PHP   1. {main}() C:\xampp\php\phpunit:0
PHP   2. require() C:\xampp\php\phpunit:41

Warning: require_once(File/Iterator/Autoload.php): failed to open stream: No such file or directory in C:\xampp\php\pear\PHPUnit\Autoload.php on line 45

Call Stack:
    0.0004     325352   1. {main}() C:\xampp\php\phpunit:0
    0.0026     366520   2. require('C:\xampp\php\pear\PHPUnit\Autoload.php')xampp\php\phpunit:41

PHP Fatal error:  require_once(): Failed opening required 'File/Iterator/Autoload.php' (include_path='.;C:\php\pear') in C:\xampp\php\pear\PHPUnit\Autoload.php on line 45
PHP Stack trace:
PHP   1. {main}() C:\xampp\php\phpunit:0'

任何人都可以解决这个问题吗？

注意：我正在使用Windows 7。

谢谢