intentional I'd say: I did not implement it, but it seems much
more logical to keep the previous rule: All *.R files in
./tests/ are run <period>
Subdirectories can be useful for organization, notably storing
test data. I don't think it's a good idea to use so very many test files
that you need subdirectories, unless maybe you are thinking
about unit tests; and then, see below.
Examples of subdirectories (some overlapping) are:
units/ - tests of minimal code modules
integration/ - tests of integrating the above units
system/ - "real-world" scenarios/use cases
requirements/ - every requirement should have at least on test.
bugs/ - every bug fix should come with a new test.
regression/ - every update should have a regression test to validate
backward compatibility etc.
robustness/ - Testing the robustness of estimators against outliers as
well as extreme parameter settings.
validation/ - validation of numeric results compared with alternative
implementations or summaries.
benchmarking/ - actually more measuring time, but can involve
validation that a method is faster than an alternative.
crossplatform/ - validate correctness across platforms.
torture/ - pushing the limits.