Add note about PHP's include_path.

Refs #2497

lib/Cake/TestSuite/templates/phpunit.php

@@ -30,6 +30,7 @@
 		<li><code>pear channel-discover pear.symfony-project.com</code></li>
 		<li><code>pear install phpunit/PHPUnit-3.5.15</code></li>
 	</ul>
+	<p>Once PHPUnit is installed make sure its located on PHP's <code>include_path</code> by checking your php.ini</p>
 	<p>For full instructions on how to <a href="http://www.phpunit.de/manual/current/en/installation.html">install PHPUnit, see the PHPUnit installation guide</a>.</p>
 	<p><a href="http://github.com/sebastianbergmann/phpunit" target="_blank">Download PHPUnit</a></p>
 </div>