Add code coverage reporting to PHPUnit configuration

Configured PHPUnit to generate a Clover coverage report. This will help track code coverage metrics and improve testing effectiveness.

Author: klapaudius

phpunit.xml.dist

@@ -28,4 +28,9 @@
             <directory suffix=".php">./src</directory>
         </include>
     </source>
+    <coverage>
+        <report>
+            <clover outputFile="phpunit.coverage.xml"/>
+        </report>
+    </coverage>
 </phpunit>