While running apicover for JCK7 in debug mode, many test classes are reported as invalid.
It's not clear whether API method invocations are couted for such classes:

Invalid class file: javasoft.sqe.tests.api.java.awt.Container.NewTests$12
java.lang.ClassFormatError: ? annotation java.lang.annotation.Retention
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.completeAnnotation(BinaryClassDescrLoader.java:971)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.readAnnotation(BinaryClassDescrLoader.java:942)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.readAnnotations(BinaryClassDescrLoader.java:929)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.read(BinaryClassDescrLoader.java:895)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:401)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:347)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.load(BinaryClassDescrLoader.java:239)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.completeAnnotation(BinaryClassDescrLoader.java:948)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.readAnnotation(BinaryClassDescrLoader.java:942)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.readAnnotations(BinaryClassDescrLoader.java:929)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader$AttrsIter.read(BinaryClassDescrLoader.java:895)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readMethods(BinaryClassDescrLoader.java:674)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:398)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:347)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.load(BinaryClassDescrLoader.java:239)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:428)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.readClass(BinaryClassDescrLoader.java:347)
at com.sun.tdk.signaturetest.loaders.BinaryClassDescrLoader.load(BinaryClassDescrLoader.java:239)
at com.sun.tdk.signaturetest.core.ClassHierarchyImpl.load(ClassHierarchyImpl.java:171)
at com.sun.tdk.signaturetest.core.ClassHierarchyImpl.load(ClassHierarchyImpl.java:167)
at com.sun.tdk.apicover.Main.check(Main.java:413)
at com.sun.tdk.apicover.Main.run(Main.java:149)
at com.sun.tdk.apicover.Main.main(Main.java:134)
This bug was moved to issue 20
https://sigtest.dev.java.net/issues/show_bug.cgi?id=20
and fixed