Fatal error: class not found in php unit test

I am trying to run phpunit manually as following from the command line in the proper directory:

phpunit UtilitiesTest UtilitiesTest.php

Yet, I get the following error message:

Fatal error: Class 'Test\dir1\dir2\Utilities' not found in
/Test/dir1/dir2/UtilitiesTest.php on line 35
Class 'Test\dir1\dir2\Utilities' not found

Line 35 is:

$retr = Utilities::toMySqlSQLStringDate($toTest);

At the beginning of UtilitiesTest.php, I have:

namespace Test\dir1\dir2;

use PHPUnit_Framework_TestCase;
use Trf\dir1\dir2\Utilities;

Yet, the file is available in a file called Utilities.class.php in Tfr\dir1\dir2\.

Does anyone know what is happening?

Update

My Utilities.class.php file begins with:

namespace Tfr\dir1\dir2;

class Utilities {
...