Path getNewOutputDir(String subdirPrefix) throws IOException {
        Path outputDir = Files.createTempDirectory(OUTPUT_ROOT, subdirPrefix);
        assert (countChildren(outputDir) == 0);
        return outputDir;
    }
helper method equivalent to File#listFiles()
grabs children only, does not walk recursively

@param p
@return
tika-batch/src/test/java/org/apache/tika/batch/fs/FSBatchTestBase.java