### Question:
HarFileSystem extends FilterFileSystem { public FileChecksum getFileChecksum(Path f) { return null; } HarFileSystem();  HarFileSystem(FileSystem fs); @Override String getScheme(); void initialize(URI name, Configuration conf); int getHarVersion(); Path getWorkingDirectory(); @Override URI getUri(); @Override Path makeQualified(Path path); @Override BlockLocation[] getFileBlockLocations(FileStatus file, long start,
                                               long len); static int getHarHash(Path p); @Override FileStatus getFileStatus(Path f); FileChecksum getFileChecksum(Path f); @Override FSDataInputStream open(Path f, int bufferSize); FSDataOutputStream create(Path f, int bufferSize); FSDataOutputStream create(Path f,
      FsPermission permission,
      boolean overwrite,
      int bufferSize,
      short replication,
      long blockSize,
      Progressable progress); @Override void close(); @Override boolean setReplication(Path src, short replication); @Override boolean delete(Path f, boolean recursive); @Override FileStatus[] listStatus(Path f); Path getHomeDirectory(); void setWorkingDirectory(Path newDir); boolean mkdirs(Path f, FsPermission permission); void copyFromLocalFile(boolean delSrc, Path src, Path dst); void copyToLocalFile(boolean delSrc, Path src, Path dst); Path startLocalOutput(Path fsOutputFile, Path tmpLocalFile); void completeLocalOutput(Path fsOutputFile, Path tmpLocalFile); void setOwner(Path p, String username, String groupname); void setPermission(Path p, FsPermission permisssion); static final int VERSION; }### Answer:
@Test public void testFileChecksum() { final Path p = new Path("har: final HarFileSystem harfs = new HarFileSystem(); Assert.assertEquals(null, harfs.getFileChecksum(p)); }