diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 3965e66..7a71ad9 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -17,4 +17,14 @@
             <directory>tests</directory>
         </testsuite>
     </testsuites>
+
+    <filter>
+        <whitelist>
+            <directory>./src</directory>
+            <exclude>
+                <directory>./tests</directory>
+                <directory>./vendor</directory>
+            </exclude>
+        </whitelist>
+    </filter>
 </phpunit>