Phpunit Test Fail

I try to test application, so I use:

phpunit functional/SiteTest.php

The Output show:


PHPUnit 3.7.10 by Sebastian Bergmann.

Configuration read from /Library/WebServer/Documents/YIIexercise/helloWorld/protected/tests/phpunit

EEE

Time: 0 seconds, Memory: 8.25Mb

There were 3 errors:

1) SiteTest::testIndex

Invalid response while accessing the Selenium Server at 'localhost:4444/selenium-server/driver/': Failed to start new browser session: org.openqa.selenium.server.RemoteCommandException: Error while launching browser

/Library/WebServer/Documents/yii/framework/test/CWebTestCase.php:63

Caused by
RuntimeException: Invalid response while accessing the Selenium Server at 'localhost:4444/selenium-server/driver/': Failed to start new browser session: org.openqa.selenium.server.RemoteCommandException: Error while launching browser

/Library/WebServer/Documents/yii/framework/test/CWebTestCase.php:63

2) SiteTest::testContact

Invalid response while accessing the Selenium Server at 'localhost:4444/selenium-server/driver/': Failed to start new browser session: org.openqa.selenium.server.RemoteCommandException: Error while launching browser

/Library/WebServer/Documents/yii/framework/test/CWebTestCase.php:63

Caused by
RuntimeException: Invalid response while accessing the Selenium Server at 'localhost:4444/selenium-server/driver/': Failed to start new browser session: org.openqa.selenium.server.RemoteCommandException: Error while launching browser

/Library/WebServer/Documents/yii/framework/test/CWebTestCase.php:63

3) SiteTest::testLoginLogout

Invalid response while accessing the Selenium Server at 'localhost:4444/selenium-server/driver/': Failed to start new browser session: org.openqa.selenium.server.RemoteCommandException: Error while launching browser

/Library/WebServer/Documents/yii/framework/test/CWebTestCase.php:63

Caused by
RuntimeException: Invalid response while accessing the Selenium Server at 'localhost:4444/selenium-server/driver/': Failed to start new browser session: org.openqa.selenium.server.RemoteCommandException: Error while launching browser

/Library/WebServer/Documents/yii/framework/test/CWebTestCase.php:63

FAILURES!
Tests: 3, Assertions: 0, Errors: 3.
aguskianto:tests aguskianto$

Is there anybody who knows what is going on?