Somehow this code still looks verbose to me. There are path expansions all over the place and I think both `phpunit-command` and `phpunit-config-file` use the same algorithm. Why not extract it into a function:

```lisp
(phpunit--first-readable-file (cabbage-project-expand-path "app" "phpunit.xml")
                              (cabbage-project-expand-path "phpunit.xml"))
```

This would express the intent behind most of the code and make it easy to add additional paths to check.