Explaining why classes are not possible in Behat as step definitions

bad_steps_proposition.php

<?php

/*

  You can't use classes like this to define steps by the simple reason:
  in Behat and Cucumber, step definitions and test contexts ARE two
  splitted logical elements, not one. Different step definitions
  can be used together in different scenarios and each scenario will
  have it's own context (environment) object. That's the main logical
  idea behind Behat - define step once - use it everywhere.

  What you've done with this example - you've tied single step
  definitions collection to environment. You've made scenario context
  by hands. And you WILL MUST create such contexts FOR EVERY scenario.
  That's insane.
  2 bad things happened here:
  1) from now on, you can't split definitions in different files,
     different directories or even use predefined definitions from multiple
     sources (inheritance woun't work, cuz there's context also).
  2) from now on, you can't easily extend environment with your own logic
     or extend context logic from different sources, cuz context now tied
     to YOUR steps (inheritance woun't work, cuz there's definitions also).

  Behat is based on 2 main concepts:
  1) global step definitions collection
  2) local context for every scenario, that gets used inside steps
  When you'll find a way to do it with PHP classes - call me.

*/

class CalcSteps
{
    protected $calc;
    protected $screen;

    public function start()
    {
        $this->calc = new Calc();
    }

    public function getSteps()
    {
        return array(
            '/I start the calculator' => array($this, 'start'),
            '/I have entered (.*) in the calculator' => array($this, 'enterValue'),
            '/I press add' => array($this, 'pressAdd'),
            '/The result should be (.*) on the screen/' => array('resultShouldBe')
        );
    }

    public function pressAdd()
    {
        $this->screen = $this->calc->getSum();
    }

    public function enterValue($value)
    {
        $this->calc->add($value);
    }

    public function resultShouldBe($value)
    {
        assertEquals($value, $this->screen);
    }
}