Symfony 1.4, set mocked Doctrine object

Im doing unit-testing with sf1.4, and want to test my model.

class TestIt extends Doctrine_Table
{
    /**
     * Returns an instance of this class.
     *
     * @return object TaskGroupTable
     */
    public static function getInstance()
    {
        return Doctrine_Core::getTable('MyTable');
    }

    /**
     * @return
     */
    public function testMe()
    {
    }
}

so I create my $mock:

$mock = $this->getMock(get_class(TestIt::getInstance()));
$mock->expects

and now I want to inject this stub. How to?