make check fails? (emacs-26.1 w/modules)

[Greg Minshall <minshall@acm.org>]

hi.  from git://git.sv.gnu.org/emacs.git i've checked out emacs-26.1.  i
configure with modules, to wit:
: ./configure --with-xwidgets --with-modules --without-dbus

"make" works, but "make check" fails:

----
  CCLD     data/emacs-module/mod-test.so
  ELC      src/emacs-module-tests.elc

In toplevel form:
src/emacs-module-tests.el:32:1:Error: Loading file /home/minshall/src/import/emacs/git/emacs/lisp/emacs-lisp/ert.elc failed to provide feature `mod-test'
Makefile:148: recipe for target 'src/emacs-module-tests.elc' failed
make[3]: *** [src/emacs-module-tests.elc] Error 1
make[3]: Target 'src/emacs-module-tests.log' not remade because of errors.
----

(i think, btw, the pointer at ".../ert.elc" is misguided; see
parenthetical a bit below.)

if i do the following:

----
mod-test-file
"/home/minshall/src/import/emacs/git/emacs/test/data/emacs-module/mod-test"

(require 'mod-test mod-test-file)
----

i get an error

----
Debugger entered--Lisp error: (error "Loading file
/usr/local/share/emacs/26.1/lisp/vc/log-edit.elc failed to provide
feature ‘mod-test’")
----

(as noted above, note the seemingly random reference to log-edit.elc.)

the only thing i notice odd is that test/data/emacs-module/mod-test.c,
when (presumably) registering, calls : provide (env, "mod-test"); rather
than some variant of Fprovide().  but, since i don't really know how
modules are expected to behave, i can't really say.

any clues would be gratefully imbibed.

cheers, Greg

ps -- if there's some politer, prettier way to interleave code/results
with e-mail text, i'd be interested to hear.  i find my style a bit hard
to parse.