如何使用 PHPSpec 扩展 PHP 函数？

require 'path/to/phpspec/vendor/autoload.php';

use PHPSpec2\ObjectBehavior;

class MyFunctionSpec extends ObjectBehavior
{
    function it_is_initializable()
    {
        $this->shouldHaveType('closure');
    }
}

class MyFunctionSpec extends ObjectBehavior
{
    function it_is_initializable()
    {
        $this->shouldHaveType('closure');
    }

    function it_accepts_array_argument()
    {
        $this->beConstructedWith([1, 2, 3]);
        $this->shouldHaveType('closure');
    }
}

function add(array $numbers)
{
    return array_sum($numbers);
}

use PHPSpec2\ObjectBehavior;

class AddFunctionSpec extends ObjectBehavior
{
    function it_is_initializable()
    {
        $this->shouldHaveType('closure');
    }

    function it_calculates_the_sum_of_numbers()
    {
        $this->beConstructedWith([1, 2, 3]);
        $this->invoke()->shouldEqual(6);
    }
}