impr: change parallel test from _test_parallel to _parallel_test

[speeddragon]

Avoid parallel test warning of function not being used, because it ends on _test_parallel and not _parallel_test. All other test helpers would also show a warning of not being used, so this fixes that.

[speeddragon]

Failed: 3. Skipped: 0. Passed: 3059.

[samcamwilliams]

Interesting... What happens if the module has -include_lib with eunit before the hb.hrl include? Or after? How do we stop these redefinitions conflicting with the eunit parse transform?

Additionally, if all we are trying to do is avoid the warning, can't we just add the exports for the test_parallel[_] functions, just like the eunit parse transform does?

[speeddragon]

Interesting... What happens if the module has -include_lib with eunit before the hb.hrl include? Or after?

eunit.hrl' included before hb.hrl' will make tests run twice.

Additionally, if all we are trying to do is avoid the warning, can't we just add the exports for the test_parallel[_] functions, just like the eunit parse transform does?

I will check that solution.