When we define and talk about test groups we sometimes treat secret and sample as if they are test groups, and sometimes as if they are not.

E.g. when defining static validators we say "Each test group may define a static validation test case.", but this definitely include secret, (and sample?, right?). OTOH, when defining result aggregation we say "in sample, secret, and any test data groups".

I think the correct definition is that "test data groups" are the things in secret, and that secret and sample are not test data groups. But in any case, we need to be consistent.

This does not really change anything, but it will make it easier to understand.