Re-Introducing PHPUnit – Getting Started with TDD in PHP
There are a lot of PHPUnit posts on our site already (just check the tag), but it's been a while since we've actually introduced people to it, and the tool has evolved significantly since then.
This article aims to re-introduce the tool in a modern way, to a modern audience, in a modern PHP environment - if you're unfamiliar with PHPUnit or testing, this post is for you.
Here we assume you're familiar with object oriented PHP and are using PHP version 7 and above. To get an environment up and running which has PHP 7 pre-installed, and to be able to follow instructions in this post to the letter without getting tripped up, we suggest you use Homestead Improved. Note also that some command line usage will be expected, but you will be guided through it all. Don't be afraid of it - it's a tool more powerful than you can imagine.
If you're wondering why we're recommending everyone use a Vagrant box, I go in depth about this in Jump Start PHP Environment, but this introduction of Vagrant will explain things adequately as well.
What exactly is Test Driven Development?
Test Driven Development is the idea that you write code in such a way that you first write another bit of code the sole purpose of which is making sure that the originally intended code works, even if it's not written yet.
Checking if something is indeed what we expect it to be is called asserting in TDD-land. Remember this term.
For example, an assertion that 2+2=4 is correct. But if we assert that 2+3=4, the testing framework (like PHPUnit) will mark this assertion as false. This is called a "failed test". We tested is 2+3 is 4, and failed. Obviously, in your application you won't be testing for sums of scalar values - instead, there'll be variables which the language will replace with real values at run-time and assert that, but you get the idea.
What is PHPUnit?
PHPUnit is a collection of utilities (PHP classes and executable files) which makes not only writing tests easy (writing tests often entails writing more code than the application actually has - but it's worth it), but also allows you to see the output of the testing process in a nice graph which lets you know about code quality (e.g. maybe there's too many IFs in a class - that's marked as bad quality because changing one condition often requires rewriting as many tests as there are IFs), code coverage (how much of a given class or function has been covered by tests, and how much remains untested), and more.
In order not to bore you with too much text (too late?), let's actually put it to use and learn from examples.
The code we end up with at the end of this tutorial can be downloaded from Github.
Bootstrapping an Example Application
To drive the examples home, we'll build a simple command line package which lets users turn a JSON file into a PHP file. That PHP file will contain the JSON data as an associative PHP array. This is just a personal use case of mine - I use Diffbot a lot and the output there can be enormous - too large to manually inspect, so easier processing with PHP can come in very handy.
Henceforth, it is assumed that you are running a fully PHP 7 capable environment with Composer installed, and can follow along. If you've booted up Homestead Improved, please SSH into it now with vagrant ssh, and let's begin.
First, we'll go into the folder where our projects live. In the case of Homestead Improved, that's Code.
cd Code
Then, we'll create a new project based on PDS-Skeleton and install PHPUnit inside it with Composer.
git clone https://github.com/php-pds/skeleton converter
cd convertTruncated by Planet PHP, read more at the original (another 7094 bytes)