public function testInvalidVirtualForeignKeys()
{
$this->specify('The Model::save with multiple virtual foreign keys and invalid entity', function () {
$body = new Body();
$body->head_1_id = null;
$body->head_2_id = 999;
// PDOException should'n be thrown
expect($body->save())->equals(false);
expect($body->getMessages())->count(1);
expect($body->getMessages()[0]->getMessage())->equals('Second head does not exists');
});
}