PHPUnit抱怨Selenium

很抱歉,如果这是微不足道的,但我没有找到任何建议如何解决这个问题.我在Ubuntu上,我的Yii项目需要PHPUnit.我已经安装了两次PHPUnit,通过下载并将phpunit.phar移动到'/ usr/local/bin'并运行:

composer global require "phpunit/phpunit=3.7.*"

现在我正在尝试执行我的Yii PHPUnit测试:

phpunit unit/DbTest.php

而我得到的是:

PHP Warning:  require_once(PHPUnit/Extensions/SeleniumTestCase.php): 
failed to open stream: No such file or directory in 
/opt/lampp/htdocs/yii-project/framework/test/CWebTestCase.php on line 12

PHP Fatal error:  require_once(): Failed opening required 
'PHPUnit/Extensions/SeleniumTestCase.php' 
(include_path='.:/usr/share/php:/usr/share/pear') in 
/opt/lampp/htdocs/yii-project/framework/test/CWebTestCase.php on line 12

所以似乎找不到PHPUnit扩展SeleniumTestCase.php.然后,PHPUnit安装手册指出Selenium'包含在PHPUnit的PHAR发行版中.' 您能建议我如何使我的Yii测试工作？