In the clover report, inner classes of test cases (*TestCase.java) are shown as source classes, i.e. they appear under the "Classes" tab in the bottom left frame instead of the "Tests" tab.
Clover's default test detection algorithm failed to distinguish the test sources. This bug was solved in Clover 2.4:
Either upgrade to the latest Clover version or in Clover for Ant use the
<testsources/> element in the
<clover-report/> task to define test sources file names.