dnspec4.php

<?php

namespace Dn;

class StringCalculatorSpec
{
    public function specification($features)
    {
        /**
         * It is initializable
         */
        $features[] = function ($calculator) {
            $calculator->shouldHaveType('StringCalculator');
        };

        /**
         * It requires string input
         */
        $features[] = function ($calculator) {
            $calculator->shouldThrow('\InvalidArgumentException')->during('add', [null]);
        };

        /**
         * It adds 2 numbers separated by comma
         */
        $features[] = function ($calculator) {
            $calculator->add('1,2')->shouldReturn(3);
        };
    }
}