Foo.php

<?php

namespace Trq;

class Foo
{
    protected function __construct()
    {
    }

    public static function create()
    {
        return new static();
    }
}

FooSpec.php

<?php

namespace spec\Trq;

use PhpSpec\ObjectBehavior;
use Prophecy\Argument;

class FooSpec extends ObjectBehavior
{
    function it_is_initializable()
    {
        $this->beConstructedThrough('create');
        $this->shouldHaveType('Trq\Foo');
    }
}

gistfile1.txt

      Trq\Foo

  10  ! is initializable
        exception [exc:ReflectionException("Access to non-public constructor of class Trq\Foo")] has been thrown.