Some tests in FileUtilsCleanDirectoryTestCase try to delete files that have been set to read-only. This is expected to throw an exception. To set the read-only flag the method chmod() tries to execute the unix "chmod" command. If this fails (which should normally be the case on windows), the test is ignored.
If Posix tools are available e.g. from Cygwin, MKS Toolkit, Microsoft's Posix Tools or similar ones the test fails.