functional testing plugin causes ClassNotResolvedException with "grails app-engine"

[Michael Greifeneder]

Configuring JDO for AppEngine
Enhancing JDO classes
  [enhance] DataNucleus Enhancer (version 1.1.4) : Enhancement of classes
  [enhance] Dec 2, 2009 9:53:55 AM org.datanucleus.metadata.MetaDataManager loadClasses
  [enhance] SEVERE: Class "functionaltestplugin.FunctionalTestCase" was not found in the CLASSPATH. Please check your specification and your CLASSPATH.
  [enhance] org.datanucleus.exceptions.ClassNotResolvedException: Class "functionaltestplugin.FunctionalTestCase" was not found in the CLASSPATH. Please check your specification and your CLASSPATH.
  [enhance] at org.datanucleus.JDOClassLoaderResolver.classForName(JDOClassLoaderResolver.java:250)
  [enhance] at org.datanucleus.JDOClassLoaderResolver.classForName(JDOClassLoaderResolver.java:415)
  [enhance] at org.datanucleus.metadata.MetaDataManager.loadClasses(MetaDataManager.java:379)
  [enhance] at org.datanucleus.enhancer.DataNucleusEnhancer.getFileMetadataForInput(DataNucleusEnhancer.java:743)
  [enhance] at org.datanucleus.enhancer.DataNucleusEnhancer.enhance(DataNucleusEnhancer.java:545)
  [enhance] at org.datanucleus.enhancer.DataNucleusEnhancer.main(DataNucleusEnhancer.java:1252)
  [enhance] at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  [enhance] at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  [enhance] at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  [enhance] at java.lang.reflect.Method.invoke(Method.java:597)
  [enhance] at com.google.appengine.tools.enhancer.Enhancer.execute(Enhancer.java:57)
  [enhance] at com.google.appengine.tools.enhancer.Enhance.<init>(Enhance.java:60)
  [enhance] at com.google.appengine.tools.enhancer.Enhance.main(Enhance.java:41)
  [enhance] Dec 2, 2009 9:53:55 AM org.datanucleus.metadata.MetaDataManager loadClasses