In "Test data / Invalid test cases / Invalid output", we currently say (and a similar point applies to "... / Valid output"):

The directory invalid_output must be organized into a tree-like structure similar to secret and may contain arguments in test_group.yaml files that are passed to the validators.

• It's unclear to me what "must be" means exactly. I think "is" would be better.
• It almost sounds like the tree-like structure must mirror the one under secret, i.e. that it must have the same groups. This is not the case, and should be clarified.