dnspec3.php

<?php

namespace Dn;

class StringCalculatorSpec
{
    public function specification($feature)
    {
        /**
         * It is initializable
         */
        $feature(function ($it) {
            $it->shouldHaveType('StringCalculator');
        });

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

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