added plugin unit tests to phpunit config

plugin unit tests are in /lib/plugins/<pluginname>/_testing

_testing/README

@@ -32,5 +32,4 @@ Bad tests are tests that do not run out of the box.
 
 
 ==== TODO ====
-  * plugin unit tests
   * integration tests (+plugins)
\ No newline at end of file

_testing/phpunit.xml

@@ -7,6 +7,9 @@
         <testsuite name="Default Unit Tests">
             <directory suffix=".test.php">unittests/</directory>
         </testsuite>
+        <testsuite name="Plugin tests">
+            <directory suffix=".test.php">../lib/plugins/*/_testing</directory>
+        </testsuite>
     </testsuites>
 
 </phpunit>