add unit/integrted tests for dpc

@thegreatwall , please change that import dpc line and pull again. 

Besides, if you use vi to open dpc.py and test_dpc.py, you will find space at the end of each line, and sometimes at the beginning of the line. That is from MS-dos. But if you open other python file, it looks neat. So please remove those space. I think that is what @tacaswell  means about unix line ending.