EUnit is the tool of choice for unit testing. Erlang.mk automates a few things on top of EUnit, including the discovery and running of unit tests.
The EUnit user guide
is the best place to learn how to write tests. Of note is
that all functions ending with
_test_ will be
picked up as EUnit test cases.
Erlang.mk will automatically pick up tests found in any of the Erlang modules of your application. It will also pick up tests located in the $(TEST_DIR) directory, which defaults to test/.
It is generally a good practice to hide test code from
the code you ship to production. With Erlang.mk, you can
do this thanks to the
TEST macro. It is only defined
when running tests:
-ifdef(TEST). %% Insert tests here. -endif.
Be careful, however, if you include the EUnit header file,
as it also defines the
TEST macro. Make sure to only include
it inside an
ifdef block, otherwise tests will always be
-ifdef(TEST). -include_lib(\"eunit/include/eunit.hrl\"). %% Insert tests here. -endif.
Erlang.mk will automatically recompile your code when you perform a normal build after running tests, and vice versa.
EUNIT_OPTS variable allows you to specify additional
EUnit options. Options are documented in the
At the time of writing, the only available option is
EUNIT_OPTS = verbose
EUNIT_ERL_OPTS variable allows you to specify options
to be passed to
erl when running EUnit tests. For example,
you can load the vm.args and sys.config files:
EUNIT_ERL_OPTS = -args_file config/vm.args -config config/sys.config
To run all tests (including EUnit):
$ make tests
To run all tests and static checks (including EUnit):
$ make check
You can also run EUnit separately:
$ make eunit
EUnit will be quiet by default, only outputting errors. You can easily make it verbose for a single invocation:
$ make eunit EUNIT_OPTS=verbose
Erlang.mk allows you to run all tests from a specific
module, or a specific test case from that module, using
For example, to run all tests from the
module (instead of all tests from the entire project),
one could write:
$ make eunit t=cow_http_hd
Similarly, to run a specific test case:
$ make eunit t=cow_http_hd:parse_accept_test_
To do the same against a multi-application repository,
you can use the
$ make -C apps/my_app eunit t=my_module:hello_test
Note that this also applies to dependencies. From Cowboy, you can run the following directly:
$ make -C deps/cowlib eunit t=cow_http_hd
Finally, code coverage is available, but covered in its own chapter.