Post-bug 370750, a number of cases that couldn't use the MOCHITEST_*FILES logic do something like: libs:: $(_TEST_FILES) $(INSTALL) $(foreach f,$^,"$f") $(DEPTH)/_tests/testing/mochitest/tests/$(subdir) The idea I have for fixing this is to extend the mochitest.mk logic to do something like: MOCHITEST_SUBDIR_FILES = ... MOCHITEST_SUBDIR = $(subdir) and then include rules.mk as normal, no libs:: rule required. I realize this doesn't generalize nicely to multiple subdirs, but individual Makefiles tend to not need to install to multiple subdirs anyway. What do people think?

FTR, I would be happy to require hg mv'ing those files to a subdir in the source, rather than complicating the build system for it; that also makes it clearer where the files end up without having to dive into makefiles.

And then you just add the subdir to MOCHITEST_FILES etc.? That would work, I suppose.

moz.build has made this obsolete.