It would be nice to be able to register test functions at runtime, in addition to the @test preprocessor behavior. Something like:

bats::register_test is_prime 2 true
bats::register_test is_prime 3 true
bats::register_test is_prime 4 false

is_prime() { .... }

#241 is closely related; it's possible implementing that would address this need. Alternatively, implementing this could be sufficient for users to construct their own parameterization on top. I'm not sure we need both features or not, but I can see them both being useful.