test: Update tests

Convert table driven tests to subtests
Tracking down a failing test starts to get difficult at some point.
Maybe when there's 10 or tests to sift through?

Add one more test for Usage func on nested Delegator

Update test documentation stuff

Improve usage tests

Simplify setup data for Delegator, Command tests
Gets too complicated to share the setup/configuration function for one
test amongst a bunch of other tests.