Download an example PHP repo, with arcconfig set to 'PhpunitTestEngine'. Example:
```
git clone https://github.com/campbsb/example-phorge-php-project.git
```
Install phpunit using composer, and test it
```
cd example-phorge-php-project
php ~/composer.phar update
phpunit
```
In a PHP phorge repo, set the following in .arcconfig:
```
"unit.engine": "PhpunitTestEngine",
"phpunit_config": "phpunit.xml",
```
Make a non-breaking change to src/Service.php (eg add a space), and run 'arc unit'