A question about the naming of e2fsprogs/tests

Hi All,

Now I am trying to create some regression tests for e2fsprogs to test
inline data feature.  I have a question about the naming of
e2fsprogs/tests.  I notice that in tests dir there are a lot of
directories, which have different prefixes, such as d_loaddump,
e_brel_bma, f_baddir, m_dasd_bs, r_move_itable, t_mmp_1on, and u_mke2fs.
As far as I can understand, d_ is for debugfs, f_ means test for filesystem,
m_ is for mke2fs, r_ is for resize2fs, t_ is for tune2fs, and u_ is for e2undo.
Could anyone tell me what e_ stands for?  If I misunderstand something, please
point it out.  Thanks.

Regards,
Zheng