erlang.mk: running multiple eunit tests

If you’re using erlang.mk, you can run a single unit test suite with make eunit t=whatever. That’s no good if you want to run multiple test suites. Here’s a nasty hack that makes it possible.

The motivation for this is that one test that fails when run as part of make eunit, but passes when run by itself.

We want to do some kind of binary chop to figure out where we’ve introduced a dependency, which means running multiple test suites. You can’t do this with t=. You can do it by subverting EUNIT_TEST_SPEC.

The first thing to do is figure out which tests are being run by default. Add a target to your top-level Makefile, after including erlang.mk:

list-tests:
	@echo $(call comma_list,$(EUNIT_MODS))

When you run it, you’ll get a comma-separated list of the test modules.

Edit that list as appropriate – e.g. you want to run the tests from a, b, c, and d – then run the following:

make eunit "EUNIT_TEST_SPEC=[a,b,c,d]"

Note the quotes and the square brackets.