testing if a method is called

I'm trying to figure out how to do a proper test about if a function is being called or not.

This function busqueda is defined within a controller AnuncioController, so I expect it being called when a user clicks on a search button which posts to anuncios/busqueda.

As far as I'm concerned, this might be done with mocks. This is what I've tried:

use \App\Http\Controllers;
class ExampleTest extends TestCase
{

   public function testSearch()
   {
        $mock_search = Mockery::mock('AnuncioController');
        $mock_search->shouldReceive('busqueda')->once()->andReturn(null); 
        $this->visit('/')->submitForm('Buscar')->seePageIs('anuncios/busqueda');

   }
}

But the assert always fails, am I using mocks wrongly?