If you get the above Exception while using testng to test your JBOSS Seam application within the Eclipse IDE, try to remove the line //<!DOCTYPE suite SYSTEM “http://beust.com/testng/testng-1.0.dtd”>// from your XML test configuration file, eg. your XML file looks like

<!DOCTYPE suite SYSTEM "http://beust.com/testng/testng-1.0.dtd" >
<suite name="testOne" verbose="2" parallel="false">
   <test name="OneTest">
     <classes>
       <class name="com.testme.OneTest"/>
     </classes>
   </test>
</suite>

Try to remove the first line. Weird, but it helped me.