Add tests for passing SafeString as

tests/Xamin/HandlebarsTest.php

@@ -576,6 +576,16 @@ class HandlebarsTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals('new', $string->getString());
     }
 
+    /**
+     * test SafeString class
+     */
+    public function testSafeStringClass()
+    {
+        $this->assertEquals('<strong>Test</strong>', $engine->render('{{string}}', array(
+            'string' => new \Handlebars\SafeString('<strong>Test</strong>')
+        )));
+    }
+
     /**
      * @param $dir
      *