Convert Zend_Db_Select into string for comparison

tests/Zend/Db/Select/TestCommon.php

@@ -1761,10 +1761,10 @@ abstract class Zend_Db_Select_TestCommon extends Zend_Db_TestSetup
     {
         $select = $this->_db->select();
         $select->from(array('p' => 'products'))->order('MD5(1);select');
-        $this->assertEquals('SELECT "p".* FROM "products" AS "p" ORDER BY "MD5(1);select" ASC', $select);
+        $this->assertEquals('SELECT "p".* FROM "products" AS "p" ORDER BY "MD5(1);select" ASC', $select->assemble());
 
         $select = $this->_db->select();
         $select->from(array('p' => 'products'))->order('name;select;MD5(1)');
-        $this->assertEquals('SELECT "p".* FROM "products" AS "p" ORDER BY "name;select;MD5(1)" ASC', $select);
+        $this->assertEquals('SELECT "p".* FROM "products" AS "p" ORDER BY "name;select;MD5(1)" ASC', $select->assemble());
     }
 }