### Question:
OffsetChannel implements StoreChannel { @Override public StoreChannel truncate( long size ) throws IOException { return delegate.truncate( offset( size ) ); } OffsetChannel( StoreChannel delegate, long offset ); @Override FileLock tryLock(); @Override void writeAll( ByteBuffer src, long position ); @Override void writeAll( ByteBuffer src ); @Override int read( ByteBuffer dst, long position ); @Override void readAll( ByteBuffer dst ); @Override void force( boolean metaData ); @Override int read( ByteBuffer dst ); @Override int write( ByteBuffer src ); @Override long position(); @Override StoreChannel position( long newPosition ); @Override long size(); @Override StoreChannel truncate( long size ); @Override void flush(); @Override long write( ByteBuffer[] srcs, int offset, int length ); @Override long write( ByteBuffer[] srcs ); @Override long read( ByteBuffer[] dsts, int offset, int length ); @Override long read( ByteBuffer[] dsts ); @Override boolean isOpen(); @Override void close();  }### Answer:
@Test void truncate() throws Exception { long size = 256; channel.truncate( size ); verify( actual ).truncate( size + offset ); }