Qafoo GmbH - passion for software quality
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

:Author: 		Benjamin Eberlei
:Date:			Tue, 08 Mar 2016 10:33:33 +0100
:Revision: 		4
:Copyright:		All rights reserved


=================================================
Testing Effects of Commands With Phake::capture()
=================================================

:Abstract:
    Today I want to share a simple trick for the excellent Mocking library
    Phake (`I wrote about it before </blog/037_phake.html>`_) when testing
    state on APIs that don't return values.

:Keywords:
    testing, mocking, phake

Today I want to share a simple trick for the excellent Mocking library `Phake
<http://phake.readthedocs.org/en/2.1/>`_ (`I wrote about it before
</blog/037_phake.html>`_) when testing state on APIs that
don't return values.

Testing becomes harder when you are using command / query separation in your
code and service operations don't return values anymore. If your command method
creates objects and passes them down the stack, then you usually want to make
assertions on the nature of the changes.

Take the following example that creates a new ``Order`` object::

    <?php

    class CheckoutHandler
    {
        private $orderRepository;
        private $productRepository;

        public function __construct($orderRepository, $productRepository)
        {
            $this->orderRepository = $orderRepository;
            $this->productRepository = $productRepository;
        }

        public function checkout(Checkout $command)
        {
            $order = new Order();
            $order->setAddress($command->address);

            foreach ($command->productIds as $id => $amount) {
                $product = $this->productRepository->find($id);
                $order->addItem($product, $amount);
            }

            $this->orderRepository->save($order);
        }
    }

A "usual" PHPUnit test for this class can only make a single assertion that the
``OrderRepository`` is called with an ``Order`` object. But we might want know
if a product was correctly assigned.

.. note::

    We can help you to set up continuous and automated testing for your
    projects. Book a `workshop`__ now.

__ /services/workshops/testing.html

With ``Phake::capture($value)`` we can assign the argument passed
to ``OrderRepository#save($order)`` to a variable that is available
inside the Unit-Test, ready to run assertions on.

::

    <?php

    class CheckoutHandlerTest extends \PHPUnit_Framework_TestCase
    {
        public function testCheckout()
        {
            $orderRepository = \Phake::mock(OrderRepository::class);
            $productRepository = \Phake::mock(ProductRepository::class);

            $product = new Product();
            \Phake::when($productRepository)->find(42)->thenReturn($product);

            $handler = new CheckoutHandler($orderRepository, $productRepository);
            $handler->checkout(new Checkout([
                'productIds' => [42 => 1],
                'address' => new Address(),
            ]));

            \Phake::verify($orderRepository)->save(\Phake::capture($order));

            $this->assertEquals(1, count($order->getProducts()));
            $this->assertSame($product, $order->getProducts()[0]);
        }
    }

See after the ``\Phake::capture($order)`` call, the ``$order`` variable
contains the argument that was passed to the OrderRepository from your code.

This argueably reaches into the tested class quite a bit, but when you use
Command / Query separation and London-Style TDD the only way to observe
behaviour and state is mocking. I still think Phake is the best mocking library
for PHP and the capture method is another good argument for it.

..
   Local Variables:
   mode: rst
   fill-column: 79
   End: 
   vim: et syn=rst tw=79


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Comments
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- Bart at Tue, 12 Apr 2016 21:11:41 +0200

  Very nice article. thx