phpunit Tests for Snippets

$x = $modx->getOption('x',$scriptProperties,'default value');
return $x;

PHP Fatal error:  Call to a member function getOption() on a non-object in 
/path/to/core/cache/includes/elements/modsnippet/556.include.cache.php on line 8

<?php
class snippetTest extends \PHPUnit_Framework_TestCase {

    // Must be static because we set it up inside a static function
    public static $modx;
    
    /**
     * Load up MODX for our tests.
     * Create sample data for testing.
     */
    public static function setUpBeforeClass() {        
        $docroot = '/set/up/magically/elsewhere';
        include_once $docroot . '/config.core.php';
        
        if (!defined('MODX_API_MODE')) {
            define('MODX_API_MODE', true);
        }
        
        include_once MODX_CORE_PATH . 'model/modx/modx.class.php';
        
        self::$modx = new \modX();
        self::$modx->initialize('mgr');
    }
    
    public function testMySnippet() {
        $props = array();
        $actual = self::$modx->runSnippet('MyTestSnippet', $props);
        $expected = 'default value';
        $this->assertEquals($expected, $actual);
    }

public function testMySnippet() {
        global $modx;
        $modx = self::$modx;

        $props = array();
        $actual = self::$modx->runSnippet('MyTestSnippet', $props);
        $expected = 'default value';
        $this->assertEquals($expected, $actual);
}

// Did not work 
global $modx;
$modx =& self::$modx;

// Did work
global $modx;
$modx = self::$modx;

/**
     * Sets up the fixture, for example, opens a network connection.
     * This method is called before each test is executed.
     */
    protected function setUp()
    {
        // echo "\n---------------- SETUP --------------------";
        require_once dirname(__FILE__) . '/build.config.php';
        require_once dirname(__FILE__) . '/uthelpers.class.php';
        require_once MODX_CORE_PATH . 'model/modx/modx.class.php';
        $this->utHelpers = new UtHelpers();

        $modx = new modX();
        $modx->initialize('mgr');
        $modx->getService('error', 'error.modError', '', '');
        $modx->getService('lexicon', 'modLexicon');
        $modx->getRequest();
        $homeId = $modx->getOption('site_start');
        $homeResource = $modx->getObject('modResource', $homeId);

        if ($homeResource instanceof modResource) {
            $modx->resource = $homeResource;
        } else {
            echo "\nNo Resource\n";
        }

        $modx->setLogLevel(modX::LOG_LEVEL_ERROR);
        $modx->setLogTarget('ECHO');

        require_once MODX_ASSETS_PATH . 'mycomponents/mycomponent/core/components/mycomponent/model/mycomponent/mycomponentproject.class.php';

        /* @var $categoryObj modCategory */
        $this->mc = new MyComponentProject($modx);
        $this->mc->init(array(), 'unittest');
        $this->modx =& $modx;