Add whitelist section to enable code coverage (#314)

Author: devmsh

phpunit.xml

@@ -19,7 +19,12 @@
             <directory suffix="Test.php">./tests/Feature</directory>
         </testsuite>
     </testsuites>
+    <filter>
+        <whitelist processUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">./src</directory>
+        </whitelist>
+    </filter>
     <php>
         <const name="STUBS_PATH" value="stubs"/>
     </php>
-</phpunit>
+</phpunit>