GetOptionKit\Option::trigger PHP Method

    public function trigger(callable $trigger)
    {
        $this->trigger = $trigger;
        return $this;
    }

 public function testTrigger()
 {
     $opt = new Option('scope');
     $opt->validValues(['public', 'private']);
     $state = 0;
     $opt->trigger(function ($val) use(&$state) {
         $state++;
     });
     $this->assertNotEmpty($opt->getValidValues());
     $opt->setValue('public');
     $this->assertEquals(1, $state);
     $opt->setValue('private');
     $this->assertEquals(2, $state);
 }