Generalize test function output

[jstokes]

Instead of tests being responsible for returning an (un)modified context map, we can make this a bit more explicit. If our create-foo function returns a test step, we could have a few options for modifying the context:

(defn create-foo
  [params]
  #::step
  {:tenant/id (step/lookup :tenant/id)
   :test
   (fn [step] ; inputs or step?
     ...
     foo-id)
   ;; option 0
   ;; nothing
   ;; option 1
   :output :foo/id
   ;; option 2
   :output (fn [ctx foo-id] (i-dont-even-know ctx :foo/id foo-id))
   })

Option 0 would be no ::step/output, meaning return the context unmodified.
Option 1 would assoc :foo/id into the context with the value foo-id.
Option 2 gives the most flexibility as a function of the input context and the returned value of the test step foo-id.