4. Testing with Common Test

4.1. Read OTP source first to learn Common Test cases

All OTP module unit tests are performed under The Common Test Framework. You need to learn the Common Test for obtaining quality assurance of including your code into OTP.

I think the easiest way to start writing Common Test cases is to read the ones already written in the OTP source. Each OTP module has the Common Test case source code under each application with the name of test/*_SUITE.erl [1]. You can find a lot of useful patterns.

Common Test manual chapter for Writing Test Suites provides a lot of useful examples, including the Test Case Groups.

4.2. Use groups for parallel and sequential tests

Common Test has the Test Case Groups, which allows programmers to enforce the sequence of executing the tests and to specify parallel execution of a set of tests.

The following code in rand module [2] explains the sequence of the tests to be performed, beginning from seed, with a group called basic_stats and the last group of reference_jump.

all() ->
  [seed, interval_int, interval_float,
   {group, basic_stats},
   plugin, measure,
   {group, reference_jump}

You need to list all the test functions and groups in all/0.

The group properties are defined in groups/0 as follows, setting parallel execution flag for each of the two groups with the test functions in the group:

groups() ->
  [{basic_stats, [parallel],
    [basic_stats_uniform_1, basic_stats_uniform_2, basic_stats_normal]},
   {reference_jump, [parallel],
    [reference_jump_state, reference_jump_procdict]}].


[1]For example, the Common Test cases for rand module is at lib/stdlib/test/rand_SUITE.erl in the OTP source code tree, since rand is a part of stdlib application.
[2]The code will be appeared on OTP 20. See https://github.com/erlang/otp/commit/1c000086275c06596ad402081be12ef95db6ea40 for the details.