diff --git a/core/phpunit.xml.dist b/core/phpunit.xml.dist
index bd0edc9..418550a 100644
--- a/core/phpunit.xml.dist
+++ b/core/phpunit.xml.dist
@@ -33,6 +33,10 @@
       <directory>./modules</directory>
       <directory>../modules</directory>
       <directory>../sites</directory>
+      <!-- by defintion Test classes have no tests. -->
+      <exclude>
+        <directory suffix="Test.php">./</directory>
+      </exclude>
      </whitelist>
   </filter>
 </phpunit>