[Libguestfs] Help: how to change default disk size when doing test

[Pino]

Hi Rich,

     I am developing a patch for btrfs enhancement: btrfs-convert. When 
I do test, run: make check tests, in dir libguestfs/tests/c-api, I got 
these error:

           0/516 test_btrfs_convert_0
     libguestfs: error: btrfs_convert: /dev/sda1: block size is too small
     conversion aborted.
     FAIL: test_btrfs_convert_0

     I also ran "btrfs-convert" command to deal with a 100MB img file 
outside the guestfish, I got the same err msg, so it is a litmitation of 
btrfs-convert

     So my question is:
         How to changed the default disk size, when do: make check tests


Yours sincerely,

Pino