@yumingfei  yeah, the testcase can be used to test disk of 'raw' type,
we can change to disk_image_format = "raw" in this .cfg file
There are 12 testcase for only 'qcow2' type already. If we add testcase for 'raw' by default, I think it is a few more testcases.
I am not sure about this, hope you can give some opinion.