public function testOffsetY()
{
$object = new Group();
$line1 = new Line(10, 20, 30, 40);
$object->addShape($line1);
$this->assertEquals(20, $object->getOffsetY());
$this->assertInstanceOf('PhpOffice\\PhpPresentation\\Shape\\Group', $object->setOffsetY(rand(1, 100)));
$this->assertEquals(20, $object->getOffsetY());
}