### Question:
FSTableDescriptors implements TableDescriptors { static String formatTableInfoSequenceId(final int number) { byte [] b = new byte[WIDTH_OF_SEQUENCE_ID]; int d = Math.abs(number); for (int i = b.length - 1; i >= 0; i--) { b[i] = (byte)((d % 10) + '0'); d /= 10; } return Bytes.toString(b); } FSTableDescriptors(final FileSystem fs, final Path rootdir);  FSTableDescriptors(final FileSystem fs, final Path rootdir,
      final boolean fsreadOnly); @Override HTableDescriptor get(final byte [] tablename); @Override HTableDescriptor get(final String tablename); @Override Map<String, HTableDescriptor> getAll(); @Override void add(HTableDescriptor htd); @Override HTableDescriptor remove(final String tablename); static boolean isTableInfoExists(FileSystem fs, Path rootdir,
      String tableName); static FileStatus getTableInfoPath(final FileSystem fs,
      final Path tabledir); static HTableDescriptor getTableDescriptor(FileSystem fs,
      Path hbaseRootDir, byte[] tableName); static HTableDescriptor getTableDescriptor(FileSystem fs, Path tableDir); static void deleteTableDescriptorIfExists(String tableName,
      Configuration conf); static boolean createTableDescriptor(final HTableDescriptor htableDescriptor,
      Configuration conf); static boolean createTableDescriptor(FileSystem fs, Path rootdir,
      HTableDescriptor htableDescriptor); static boolean createTableDescriptor(FileSystem fs, Path rootdir,
      HTableDescriptor htableDescriptor, boolean forceCreation); static boolean createTableDescriptorForTableDirectory(FileSystem fs, Path tabledir,
      HTableDescriptor htableDescriptor, boolean forceCreation); static final String TABLEINFO_NAME; }### Answer:
@Test public void testFormatTableInfoSequenceId() { Path p0 = assertWriteAndReadSequenceid(0); StringBuilder sb = new StringBuilder(); for (int i = 0; i < FSTableDescriptors.WIDTH_OF_SEQUENCE_ID; i++) { sb.append("0"); } assertEquals(FSTableDescriptors.TABLEINFO_NAME + "." + sb.toString(), p0.getName()); Path p2 = assertWriteAndReadSequenceid(2); Path p10000 = assertWriteAndReadSequenceid(10000); Path p = new Path(p0.getParent(), FSTableDescriptors.TABLEINFO_NAME); FileStatus fs = new FileStatus(0, false, 0, 0, 0, p); FileStatus fs0 = new FileStatus(0, false, 0, 0, 0, p0); FileStatus fs2 = new FileStatus(0, false, 0, 0, 0, p2); FileStatus fs10000 = new FileStatus(0, false, 0, 0, 0, p10000); FSTableDescriptors.FileStatusFileNameComparator comparator = new FSTableDescriptors.FileStatusFileNameComparator(); assertTrue(comparator.compare(fs, fs0) > 0); assertTrue(comparator.compare(fs0, fs2) > 0); assertTrue(comparator.compare(fs2, fs10000) > 0); }