Validation in controller for "patch" request

Hello!
I want to add "update" action to controller as patch.
I've created this test:

PHP Code:

$attributes = ['title' => 'Changed Title'];
$response = $this->patch(route_to('project.update', 1), $attributes); 


Now the only method to retrieve data in controller is:

PHP Code:

$this->request->getVar(['title']); 


I.e. data are not in POST array. This is ok until I try to run validation:

PHP Code:

$this->validate(['title' => 'required|min_length[3]|max_length[128]']);
$e = $this->validator->getErrors(); 


Now $e has message that "The title field is required". I.e. validation does not see passed data.
When I change action type to post it works as expected.
Is there any way to implement validation for patch or I have to use post? What are correct tests if patch can be used?