refactor: remove builder class and use concrete class

tests: added more unit tests for event processor

tests/bootstrap.php

@@ -0,0 +1,13 @@
+<?php
+
+$loader = require __DIR__ . '/../vendor/autoload.php';
+if (!$loader) {
+    die(<<<'EOT'
+You must set up the project dependencies, run the following command:
+composer install
+EOT
+    );
+}
+
+return $loader;
+