Joseph Wright writes:
 > On 18/12/2010 01:31, Philipp Stephani wrote:
 > > Hello,
 > >
 > > lines 1377 to 1383 of l3tl.dtx read
 > >
 > >      \tex_ifx:D \l_tl_tmpa_tl \l_tl_tmpb_tl
 > >        \group_end:
 > >        \prg_return_false:
 > >      \tex_else:D
 > >        \group_end:
 > >        \prg_return_false:
 > >      \tex_fi:D
 > >
 > > The first \prg_return_false: should be \prg_return_true:.
 > >
 > > Regards,
 > > Philipp
 > >
 > 
 > Fixed in the SVN: CTAN update upcoming.

looks like we should look at completing unit tests for the core modules. 

Any volunteer to help here?

(quite a number are already there (under /testfiles directory) but as this bug
shows not all functions are sufficiently tested yet)

frank