Clojurians Log v2

I've been reminding myself how to use spec and one thing I can't remember is how to get better errors from this sort of thing?

(defn load-order [order-book {:keys [side id] :as order}]
  {:pre [(s/valid? :order/order order)]}
  (assoc-in order-book [side id] order))

Which does give me this:

Execution error (AssertionError) at fruit-economy.sim.market/load-order (market.clj:23).
Assert failed: (is (s/valid? :order/order order))

But considering it's a spec, I was expecting a little more? I've hacked it a bit by wrapping it in an is, which gives me:

FAIL in () (market.clj:2)
expected: (s/valid? :order/order order)
  actual: (not
           (s/valid?
            :order/order
            {:price 1,
             :size 425.0,
             :side :sell,
             :id 10229,
             :good-kw :inventory}))

But I'm sure there's a better way? EDIT: @jcf suggested using fdef to specify args and instrument, so I've swapped to doing that and calling instrument on debug as so in my core ns:

(when (debug?)
  (let [instrument (requiring-resolve 'clojure.spec.test.alpha/instrument)]
    (instrument 'fruit-economy.sim.market/load-order)))

To be honest this is pretty great, but perhaps there's something I'm missing? So I thought I'd pop the question here! REF: https://github.com/Folcon/fruit-economy/commit/a92b4b5329eabd7347240804f04224b6440ebdb2