What are some common errors or issues that users may encounter when setting up PHPUnit in Aptana?

One common issue users may encounter when setting up PHPUnit in Aptana is a "Class 'PHPUnit_Framework_TestCase' not found" error. This can be solved by including the PHPUnit autoloader in your test file before extending PHPUnit_Framework_TestCase.

require_once 'path/to/vendor/autoload.php';

class YourTestClass extends PHPUnit_Framework_TestCase {
    // Your test methods here
}