Chris Hartjes - The Grumpy Programmers Guide To Building Testable PHP Applications

There is no denying that the PHP world has finally caught up with other programmingcommunities in terms of its attitude towards testing. As a result, you can find a lotof really good resources either online or in book form from your favourite retailer.

Most of this information focuses on the actual writing of tests and strategies forthe type of tests you need to write. What I found was missing from most of theseresources was how to write applications that you could actually test. Sounds likesomething obvious, at least to me.

There is an open secret out there: some applications can never be tested with automatedtesting tools. Theyre built in such a manner that you couldnt wrap anything beyondtests that examine the HTML output from it. Thats really a shame, because these sortof things dont happen on purpose. Like technical debt in your code, it builds up overtime and at some point you end up with an application that might as well be a black box: youput inputs into it and you get output back, and have no easy way to determine how tofix things if it sends you back something you dont expect.

But make no mistake: building a non-trivial testable application is somethingthat actually takes experience. A lot of experience. You will mess up. Youwill need to refactor things at a later point, and will often find that refactoringto be painful when contrasted with the seemingly-simple feature request that youare trying to implement.

I am a big believer in the power of automated testing to give you an application thatis maintainable, extendible and performant. I dont always get to work on applicationsthat have made a commitment to be testable. It really is a different way of lookingat the entire process of testing. Its one thing to know how to write an assertionstatement, or understand how to use mock objects to isolate components of a modulethat you are trying to test. Its another to have to create an application that lets you test it from end to end.

I am hoping to pass on my thoughts on building applications that you can easily test,and show you some of the techniques that I use to try and make the job easier. In thisguide you will learn about creating the proper environment for your application, aprogramming concept known as Dependency Injection, and some best practices fortesting the output of your application from the command line.

I really think that an optimal architecture for a web application is to buildsmall modules of code that you then integrate together to solve larger problems.There is no other magic bullet to build a complicated system. I have run across anold saying (that I have been unable to find an attribution for) that says simple systems can display complex behaviour but complexsystems can only display simple behaviour.

Keep your modules, components, libraries, whatever you decide to call them small, readable, and easy to verify that they work as desired in isolationor when integrated together. That way you will have an application that isvery easy to write tests for and provide you with some protection againstregression errors and other unexpected bumps in the road.

The goal is always the same: create a workflow that shortens the time it takesfor code to make it from your text editor of choice all the way into productionwith the fewest bugs possible.