Replace outdated test setup code with composer.json

Also, we could require our PHP libraries as soon as we have uploaded them to
Packagist.

Author: lippserd

.gitignore

@@ -6,9 +6,6 @@
 !.travis.yml
 !.mailmap
 
-# Testing - created by test/setup_vendor.sh
-/vendor/
-
 # Exclude application log files
 var/log/*
 
@@ -20,3 +17,7 @@ build/*
 # Exclude dompdf font cache
 library/vendor/dompdf/lib/fonts/*.php
 library/vendor/dompdf/lib/fonts/log.htm
+
+# Exclude files from composer install
+vendor/
+composer.lock

composer.json

@@ -0,0 +1,10 @@
+{
+  "config": {
+    "platform": {
+      "php": "8.2"
+    }
+  },
+  "require-dev": {
+    "mockery/mockery": "^1.6"
+  }
+}