Inheritance: extends HasOneOrMany
 public function testTouchMethodUpdatesRelatedTimestamps()
 {
     $builder = m::mock('LMongo\\Eloquent\\Builder');
     $parent = m::mock('LMongo\\Eloquent\\Model');
     $parent->shouldReceive('getKey')->andReturn(1);
     $builder->shouldReceive('getModel')->andReturn($related = m::mock('StdClass'));
     $builder->shouldReceive('where');
     $relation = new HasOne($builder, $parent, 'foreign_key');
     $related->shouldReceive('getTable')->andReturn('table');
     $related->shouldReceive('getUpdatedAtColumn')->andReturn('updated_at');
     $builder->shouldReceive('update')->once()->with(array('updated_at' => new MongoDate()));
     $relation->touch();
 }