The Common Test user guide is the best place to learn how to write tests. Erlang.mk requires that file names for test suites end with _SUITE.erl and that the files be located in the $(TEST_DIR) directory. This defaults to test/.

The CT_OPTS variable allows you to set extra Common Test options. Options are documented in the Common Test user guide. You can use it to set Common Test hooks, for example:

CT_OPTS = -ct_hooks cowboy_ct_hook

The CT_SUITES variable can be used to override what Common Test suites Erlang.mk will be aware of. It does not normally need to be set as Erlang.mk will find the test suites automatically.

The name of the suite is the part before _SUITE.erl. If the file is named http_SUITE.erl, the test suite is http:

CT_SUITES = http ws

The CT_LOGS_DIR variable can be used to set where HTML log files are to be written. This defaults to logs/.

CT_LOGS_DIR = ct_output_log_dir

To run all tests (including Common Test):

$ make tests

To run all tests and static checks (including Common Test):

$ make check

You can also run Common Test separately:

$ make ct

Erlang.mk will create targets for all test suites it finds. If you have a file named test/http_SUITE.erl, then the target ct-http will run that specific test suite:

$ make ct-http

Erlang.mk provides a convenient way to run a specific group or a specific test case within a specific group, using the variable t. Note that this only applies to suite-specific targets, like the ct-http example above.

To run all tests from the http_compress group in the http_SUITE test suite, write:

$ make ct-http t=http_compress

Similarly, to run a specific test case in that group:

$ make ct-http t=http_compress:headers_dupe

To do the same against a multi-application repository, you can use the -C option:

$ make -C apps/my_app ct-http t=my_group:my_case

Note that this also applies to dependencies. When using Cowboy as a dependency, you can run the following directly:

$ make -C deps/cowboy ct-http t=http_compress

The variable c can be used to run a specific test when the test suite does not group test cases:

$ make ct-http c=headers_dupe

A test within a specific subgroup can be run by providing a group path:

$ make ct-http t=[top_level_group,second_level_group,third_level_group]:my_case

Finally, code coverage is available, but covered in its own chapter.