1. Put the ashcroft jar on the classpath for the chosen JUnit launch configuration
2. Add

   -Djava.security.manager=com.thoughtworks.ashcroft.runtime.JohnAshcroft

   to the JVM arguments on the Arguments tab.
   
   
   
   
3. Run some naughty tests and see them fail
   
   
   
   

Also see Ashcroft Configuration for a full list of configuration options.