### Question:
DiffScriptBackupWriter implements BackupWriter { @Override public void writeChunk(long start, int length) throws IOException { mWriter.writeChunk(start, length); mBytesWritten += length; } @VisibleForTesting  DiffScriptBackupWriter(SingleStreamDiffScriptWriter writer); static DiffScriptBackupWriter newInstance(OutputStream outputStream); @Override void writeBytes(byte[] bytes); @Override void writeChunk(long start, int length); @Override long getBytesWritten(); @Override void flush();  }### Answer:
@Test public void writeChunk_writesChunkToWriter() throws Exception { mBackupWriter.writeChunk(0, 10); verify(mDiffScriptWriter).writeChunk(0, 10); }