diff --git a/README.md b/README.md
index 0119e2c..47d3b4a 100644
--- a/README.md
+++ b/README.md
@@ -106,7 +106,7 @@ An example of using the GUI:
 
 Coverage looks like this if you run `lein cloverage`:
 
-![test_coverage_2024-02-15_10-13.png](screenshots%2Ftest_coverage_2024-02-15_10-13.png)
+![test_coverage_2024-02-16_11-15.png](screenshots%2Ftest_coverage_2024-02-16_11-15.png)
 
 ## How It Works
 
diff --git a/nomis-ns-graph.png b/nomis-ns-graph.png
index a362612..90347ce 100644
Binary files a/nomis-ns-graph.png and b/nomis-ns-graph.png differ
diff --git a/project.clj b/project.clj
index 1abcde1..4aac8c2 100644
--- a/project.clj
+++ b/project.clj
@@ -5,6 +5,7 @@
             :url  "https://www.eclipse.org/legal/epl-2.0/"}
   :dependencies [[org.clojure/clojure "1.11.1"]
                  [org.clojure/core.async "1.6.681"]
+                 [metosin/malli "0.14.0"]
 
                  [org.clojure/tools.cli "1.0.219"]
 
diff --git a/screenshots/test_coverage_2024-02-16_11-15.png b/screenshots/test_coverage_2024-02-16_11-15.png
new file mode 100644
index 0000000..82d12f7
Binary files /dev/null and b/screenshots/test_coverage_2024-02-16_11-15.png differ
diff --git a/src/closyr/core.clj b/src/closyr/core.clj
index a948f15..edea976 100644
--- a/src/closyr/core.clj
+++ b/src/closyr/core.clj
@@ -3,8 +3,8 @@
   (:require
     [clojure.string :as str]
     [clojure.tools.cli :as cli]
-    [closyr.dataset.csv :as input-csv]
-    [closyr.log :as log]
+    [closyr.util.csv :as input-csv]
+    [closyr.util.log :as log]
     [closyr.symbolic-regression :as symreg])
   (:import
     (java.io
diff --git a/src/closyr/ga.clj b/src/closyr/ga.clj
index 412cb01..d06cf42 100644
--- a/src/closyr/ga.clj
+++ b/src/closyr/ga.clj
@@ -1,8 +1,8 @@
 (ns closyr.ga
   (:refer-clojure :exclude [rand rand-int rand-nth shuffle])
   (:require
-    [closyr.log :as log]
-    [closyr.dataset.prng :refer :all]))
+    [closyr.util.log :as log]
+    [closyr.util.prng :refer :all]))
 
 
 (set! *warn-on-reflection* true)
diff --git a/src/closyr/ops.clj b/src/closyr/ops.clj
index bd887c4..db1ee74 100644
--- a/src/closyr/ops.clj
+++ b/src/closyr/ops.clj
@@ -3,11 +3,12 @@
   (:require
     [clojure.core.async :as async :refer [go go-loop timeout <!! >!! <! >! chan put! take! alts!! alts! close!]]
     [clojure.string :as str]
-    [closyr.dataset.prng :refer :all]
-    [closyr.log :as log]
+    [closyr.util.prng :refer :all]
+    [closyr.util.log :as log]
     [closyr.ops.common :as ops-common]
     [closyr.ops.eval :as ops-eval]
-    [closyr.ops.modify :as ops-modify])
+    [closyr.ops.modify :as ops-modify]
+    [closyr.util.spec :as specs])
   (:import
     (java.text
       DecimalFormat)
@@ -74,7 +75,9 @@
       (and (number? n) (Double/isNaN n))))
 
 
-(defn- compute-residual
+(defn compute-residual
+  "Compute the residual (difference) between 2 number (y-values)"
+  {:malli/schema [:=> [:cat number? number?] number?]}
   [expected actual]
   (let [res (if (not-finite? actual)
               max-resid
@@ -281,6 +284,7 @@
 
       (reset! test-timer* (Date.))
       (log/info i "-step pop size: " pop-size
+                " points: " (count input-ys-vec)
                 " max leafs: " max-leafs
                 " took secs: " took-s
                 " phenos/s: " (Math/round ^double (/ (* pop-size *log-steps*) took-s))
@@ -303,3 +307,6 @@
                              :best-p95-score        (:score best-p95-v)
                              :best-p90-score        (:score best-p90-v)}))))
   (reset! sim-stats* {}))
+
+
+(specs/instrument-all!)
diff --git a/src/closyr/ops/common.clj b/src/closyr/ops/common.clj
index 0c7c5d0..027cc8e 100644
--- a/src/closyr/ops/common.clj
+++ b/src/closyr/ops/common.clj
@@ -2,8 +2,9 @@
   (:refer-clojure :exclude [rand rand-int rand-nth shuffle])
   (:require
     [clojure.core.async :as async :refer [go go-loop timeout <!! >!! <! >! chan put! take! alts!! alt!! close!]]
-    [closyr.dataset.prng :refer :all]
-    [closyr.log :as log])
+    [closyr.util.prng :refer :all]
+    [closyr.util.log :as log]
+    [closyr.util.spec :as specs])
   (:import
     (java.util
       Date
@@ -257,6 +258,7 @@
 
 (defn extend-xs
   "Add extra xs on either side of the provided range"
+  {:malli/schema [:=> [:cat [:sequential number?]] map?]}
   [input-xs-vec]
   (let [x-min                (first input-xs-vec)
         x-max                (last input-xs-vec)
@@ -284,3 +286,6 @@
      :x-head-list x-head-list
      :x-tail      x-tail
      :x-tail-list x-tail-list}))
+
+
+(specs/instrument-all!)
diff --git a/src/closyr/ops/eval.clj b/src/closyr/ops/eval.clj
index 2584d5f..ffe1bc7 100644
--- a/src/closyr/ops/eval.clj
+++ b/src/closyr/ops/eval.clj
@@ -1,7 +1,8 @@
 (ns closyr.ops.eval
   (:require
-    [closyr.log :as log]
-    [closyr.ops.common :as ops-common])
+    [closyr.util.log :as log]
+    [closyr.ops.common :as ops-common]
+    [closyr.util.spec :as specs])
   (:import
     (org.matheclipse.core.eval
       EvalControlledCallable
@@ -38,6 +39,7 @@
 
 (defn ^IExpr eval-phenotype-on-expr-args
   "Eval an expr at every point in the args"
+  {:malli/schema [:=> [:cat #'specs/GAPhenotype some?] any?]}
   [{^IAST expr :expr ^ISymbol x-sym :sym ^ExprEvaluator util :util p-id :id :as pheno}
    ^"[Lorg.matheclipse.core.interfaces.IExpr;" expr-args]
   (try
@@ -90,8 +92,9 @@
 
 (defn eval-vec-pheno
   "Evaluate a phenotype's expr on input xs/ys vecs"
+  {:malli/schema [:=> [:cat #'specs/GAPhenotype #'specs/SolverEvalArgs] [:or [:vector number?] nil?]]}
   [p
-   {:keys [input-xs-list input-xs-count input-ys-vec]
+   {:keys [input-xs-list input-xs-count]
     :as   run-args}]
   (let [^IExpr new-expr (:expr p)
         ^IExpr eval-p   (eval-phenotype-on-expr-args p input-xs-list)]
@@ -164,3 +167,6 @@
 
     {:xs xs
      :ys evaluated-ys}))
+
+
+(specs/instrument-all!)
diff --git a/src/closyr/ops/initialize.clj b/src/closyr/ops/initialize.clj
index 69f731f..76f5824 100644
--- a/src/closyr/ops/initialize.clj
+++ b/src/closyr/ops/initialize.clj
@@ -1,7 +1,8 @@
 (ns closyr.ops.initialize
   (:require
-    [closyr.log :as log]
-    [closyr.ops.common :as ops-common])
+    [closyr.util.log :as log]
+    [closyr.ops.common :as ops-common]
+    [closyr.util.spec :as specs])
   (:import
     (org.matheclipse.core.expression
       AST
@@ -21,6 +22,7 @@
 
 (defn initial-phenotypes
   "Initial exprs scaled up in quantity to use in GA evolution"
+  {:malli/schema [:=> [:cat pos-int?] #'specs/GAPopulationPhenotypes]}
   [p-count]
   (let [^ISymbol x ops-common/sym-x]
     (->>
@@ -31,6 +33,7 @@
 
 (defn initial-mutations
   "All mutations to use in GA evolutions"
+  {:malli/schema [:=> [:cat] [:vector #'specs/GAMutation]]}
   []
   [{:op          :modify-fn
     :label       "Derivative"
@@ -61,8 +64,8 @@
     :modifier-fn (fn ^IExpr [{^IAST expr :expr ^ISymbol x-sym :sym :as pheno}]
                    (F/Plus expr (F/Divide 1 F/C100)))}
 
-   {:op         :modify-fn
-    :label      "-1/100"
+   {:op          :modify-fn
+    :label       "-1/100"
     :modifier-fn (fn ^IExpr [{^IAST expr :expr ^ISymbol x-sym :sym :as pheno}]
                    (F/Subtract expr (F/Divide 1 F/C100)))}
 
@@ -659,3 +662,6 @@
                         (if (ops-common/should-modify-branch leaf-count pheno)
                           (F/Subtract ie (F/num 0.1))
                           ie))}])
+
+
+(specs/instrument-all!)
diff --git a/src/closyr/ops/modify.clj b/src/closyr/ops/modify.clj
index 8e17acc..72bb871 100644
--- a/src/closyr/ops/modify.clj
+++ b/src/closyr/ops/modify.clj
@@ -3,9 +3,10 @@
   (:require
     [clojure.core.async :as async :refer [go go-loop timeout <!! >!! <! >! chan put! take! alts!! alt!! close!]]
     [clojure.string :as str]
-    [closyr.dataset.prng :refer :all]
-    [closyr.log :as log]
-    [closyr.ops.common :as ops-common])
+    [closyr.ops.common :as ops-common]
+    [closyr.util.log :as log]
+    [closyr.util.prng :refer :all]
+    [closyr.util.spec :as specs])
   (:import
     (java.util.function
       Function)
@@ -139,6 +140,17 @@
 
 (defn crossover
   "Do phenotype crossover on their expr AST"
+  {:malli/schema
+   [:=>
+
+    ;; inputs:
+    [:cat
+     pos-int?
+     #'specs/GAPhenotype
+     #'specs/GAPhenotype]
+
+    ;; outputs:
+    #'specs/GAPhenotype]}
   [max-leafs
    {^IAST e1 :expr ^ISymbol x-sym :sym ^ExprEvaluator util :util :as p}
    {^IAST e2 :expr :as p-discard}]
@@ -184,6 +196,23 @@
 
 (defn apply-modifications
   "Apply a sequence of modifications"
+  {:malli/schema
+   [:=>
+
+    ;; inputs:
+    [:cat
+     pos-int?
+     pos-int?
+     [:sequential #'specs/GAMutation]
+     #'specs/GAPhenotype
+     #'specs/GAPhenotype]
+
+    ;; outputs:
+    [:map {:closed true}
+     [:new-pheno #'specs/GAPhenotype]
+     [:iters int?]
+     [:mods [:sequential #'specs/GAMutation]]]]}
+
   [max-leafs mods-count initial-muts p-winner p-discard]
   (loop [iters              0
          mods-left-to-apply mods-count
@@ -237,26 +266,29 @@
     (concat (repeat 40 1))
     (concat (repeat 30 2))
     (concat (repeat 20 3))
-    (concat (repeat 18 4))
-    (concat (repeat 16 5))
-    (concat (repeat 15 6))
-    (concat (repeat 14 7))
-    (concat (repeat 13 8))
-    (concat (repeat 12 9))
-    (concat (repeat 11 10))
-    (concat (repeat 10 11))
-    (concat (repeat 9 12))
-    (concat (repeat 8 13))
-    (concat (repeat 7 14))
-    (concat (repeat 6 15))
-    (concat (repeat 5 16))
-    (concat (repeat 4 17))
-    (concat (repeat 3 18))
-    (concat (repeat 2 19))
-    (concat (repeat 1 20))
+    (concat (repeat 15 4))
+    (concat (repeat 12 5))
+    (concat (repeat 10 6))
+    (concat (repeat 9 7))
+    (concat (repeat 8 8))
+    (concat (repeat 7 9))
+    (concat (repeat 6 10))
+    (concat (repeat 5 11))
+    (concat (repeat 4 12))
+    (concat (repeat 3 13))
+    (concat (repeat 2 14))
+    (concat (repeat 1 15))
+    ;; (concat (repeat 5 16))
+    ;; (concat (repeat 4 17))
+    ;; (concat (repeat 3 18))
+    ;; (concat (repeat 2 19))
+    ;; (concat (repeat 1 20))
     ;; (concat (repeat 3 21))
     ;; (concat (repeat 2 22))
     ;; (concat (repeat 1 23))
     ;; (concat (repeat 1 24))
     ;; (concat (repeat 1 25))
     vec))
+
+
+(specs/instrument-all!)
diff --git a/src/closyr/symbolic_regression.clj b/src/closyr/symbolic_regression.clj
index 54f7c41..abad4e5 100644
--- a/src/closyr/symbolic_regression.clj
+++ b/src/closyr/symbolic_regression.clj
@@ -2,12 +2,14 @@
   (:require
     [clojure.core.async :as async :refer [go go-loop timeout <!! >!! <! >! chan put! take! alts!! alts! close!]]
     [closyr.ga :as ga]
-    [closyr.log :as log]
+    [closyr.util.log :as log]
     [closyr.ops :as ops]
     [closyr.ops.common :as ops-common]
     [closyr.ops.initialize :as ops-init]
+    [closyr.util.spec :as specs]
     [closyr.ui.gui :as gui]
     [flames.core :as flames]
+    [malli.core :as m]
     [seesaw.core :as ss])
   (:import
     (java.util
@@ -466,6 +468,8 @@
 
   (init
     [this]
+    (specs/validate! "SolverRunConfig" specs/SolverRunConfig run-config)
+    (specs/validate! "SolverRunArgs" specs/SolverRunArgs run-args)
     (let [{:keys [iters initial-phenos initial-muts use-gui?]} run-config
           start    (print-and-save-start-time iters initial-phenos)
           init-pop (ga/initialize
@@ -476,7 +480,8 @@
 
       (log/info "Running with logging every n steps: " (:log-steps run-config))
 
-      (assoc this :ga-result init-pop
+      (assoc this
+             :ga-result init-pop
              :iters-to-go iters
              :start-ms start)))
 
@@ -488,10 +493,13 @@
           iters-to-go (:iters-to-go this)]
       (binding [ops/*log-steps* log-steps]
         (if (zero? iters-to-go)
-          (assoc this :status :done :result {:iters-done       (- iters iters-to-go)
-                                             :final-population population
-                                             :next-step        :wait})
+          (assoc this
+                 :status :done
+                 :result {:iters-done       (- iters iters-to-go)
+                          :final-population population
+                          :next-step        :wait})
           (let [{scores :pop-scores :as ga-result} (ga/evolve population)]
+            (specs/validate! "GAPopulation" specs/GAPopulationPhenotypes (:pop ga-result))
             (ops/report-iteration iters-to-go iters ga-result run-args run-config)
             (assoc this :ga-result ga-result :iters-to-go (next-iters iters-to-go scores)))))))
 
@@ -534,11 +542,10 @@
     return-value))
 
 
-(defn- run-ga-iterations-using-record
+(defn run-ga-iterations-using-record
   "Run GA evolution iterations on initial population"
-  [{:keys [iters initial-phenos initial-muts use-gui?] :as run-config}
-   run-args]
-
+  {:malli/schema [:=> [:cat #'specs/SolverRunConfig #'specs/SolverRunArgs] #'specs/SolverRunResults]}
+  [run-config run-args]
   (loop [solver-state (init (map->SolverStateController {:run-config run-config :run-args run-args}))]
     (let [[recur? next-solver-state] (run-iteration solver-state)]
       (if recur?
@@ -700,8 +707,22 @@
     (System/exit 0)))
 
 
+(def ^:private CLIArgs
+  [:map
+   {:closed true}
+   [:log-level {:optional true} keyword?]
+   [:iterations any?]
+   [:population any?]
+   [:headless any?]
+   [:xs {:optional true} any?]
+   [:ys {:optional true} any?]
+   [:use-flamechart {:optional true} any?]
+   [:max-leafs {:optional true} any?]])
+
+
 (defn run-app-from-cli-args
   "Run app from CLI args"
+  {:malli/schema [:=> [:cat #'CLIArgs] #'specs/SolverRunResults]}
   [{:keys [iterations population headless xs ys use-flamechart max-leafs] :as cli-opts}]
   (log/info "CLI: run from options: " cli-opts)
   (let [run-config {:initial-phenos (ops-init/initial-phenotypes population)
@@ -722,6 +743,11 @@
     result))
 
 
+;; todo: feel kind of hacky to have to call this in ?every? ns that has defn schema
+(specs/instrument-all!)
+
+
+(comment (println "FN SCHEMAS: " (m/function-schemas)))
 (comment (macroexpand-1 `(log/info "Hello")))
 (comment (log/info "Hello"))
 (comment (run-app-without-gui))
diff --git a/src/closyr/ui/gui.clj b/src/closyr/ui/gui.clj
index c9f240a..1a44ab7 100644
--- a/src/closyr/ui/gui.clj
+++ b/src/closyr/ui/gui.clj
@@ -2,9 +2,9 @@
   (:require
     [clojure.core.async :as async :refer [go go-loop timeout <!! >!! <! >! chan put! alts!]]
     [clojure.java.io :as io]
-    [closyr.dataset.csv :as input-csv]
+    [closyr.util.csv :as input-csv]
     [closyr.dataset.inputs :as input-data]
-    [closyr.log :as log]
+    [closyr.util.log :as log]
     [closyr.ui.plot :as plot]
     [seesaw.behave :as sb]
     [seesaw.border :as sbr]
@@ -455,7 +455,7 @@
 (defn- settings-max-leafs-on-change
   [^MouseEvent e]
   (let [b (.getText ^JRadioButtonMenuItem (.getSource e))]
-    (swap! experiment-settings* assoc :max-leafs (Double/parseDouble b))
+    (swap! experiment-settings* assoc :max-leafs (Integer/parseInt b))
     (log/info "max leafs changed to " b)))
 
 
diff --git a/src/closyr/dataset/csv.clj b/src/closyr/util/csv.clj
similarity index 96%
rename from src/closyr/dataset/csv.clj
rename to src/closyr/util/csv.clj
index 714fa67..445071d 100644
--- a/src/closyr/dataset/csv.clj
+++ b/src/closyr/util/csv.clj
@@ -1,8 +1,8 @@
-(ns closyr.dataset.csv
+(ns closyr.util.csv
   (:require
     [clojure.data.csv :as csv]
     [clojure.java.io :as io]
-    [closyr.log :as log]))
+    [closyr.util.log :as log]))
 
 
 (set! *warn-on-reflection* true)
diff --git a/src/closyr/log.clj b/src/closyr/util/log.clj
similarity index 99%
rename from src/closyr/log.clj
rename to src/closyr/util/log.clj
index 611e92a..5c3bc92 100644
--- a/src/closyr/log.clj
+++ b/src/closyr/util/log.clj
@@ -1,4 +1,4 @@
-(ns closyr.log
+(ns closyr.util.log
   (:require
     [clojure.pprint :as pprint]
     [clojure.string :as str])
diff --git a/src/closyr/dataset/prng.clj b/src/closyr/util/prng.clj
similarity index 98%
rename from src/closyr/dataset/prng.clj
rename to src/closyr/util/prng.clj
index 402e74f..247c854 100644
--- a/src/closyr/dataset/prng.clj
+++ b/src/closyr/util/prng.clj
@@ -1,4 +1,4 @@
-(ns closyr.dataset.prng
+(ns closyr.util.prng
   (:refer-clojure :exclude [rand rand-int rand-nth shuffle])
   (:import
     (clojure.lang
diff --git a/src/closyr/util/spec.clj b/src/closyr/util/spec.clj
new file mode 100644
index 0000000..57324de
--- /dev/null
+++ b/src/closyr/util/spec.clj
@@ -0,0 +1,115 @@
+(ns closyr.util.spec
+  (:require
+    [clojure.pprint :as pp]
+    [closyr.util.log :as log]
+    [malli.core :as m]
+    [malli.error :as me]
+    [malli.instrument :as mi]))
+
+
+(def ^:dynamic *check-schema*
+  "Toggle checking schema and potentially throwing exceptions"
+  true)
+
+
+(defn validate!
+  "Check that an object o is compliant with schema s with name n, or throw exception"
+  [n s o]
+  (when (and *check-schema* (not (m/validate s o)))
+    (let [explained (me/humanize (m/explain s o))]
+      (log/error "Error in input schema: " n)
+      (pp/pprint [n explained])
+      (throw (Exception. (str "Error, input failed schema: " [n explained])))))
+  true)
+
+
+(defn instrument-all!
+  "Instrument all defn schema"
+  []
+  (when *check-schema*
+    (mi/collect!)
+    (mi/instrument!)))
+
+
+#_(defn- disable-validate-instrumentation!
+  "Turn off all schema checks"
+  []
+  (alter-var-root #'*check-schema* (constantly false))
+  (mi/unstrument!
+    {:filters [(apply mi/-filter-ns (concat (keys (m/function-schemas))
+                                            ['closyr.util.spec-test
+                                             'cursive.tests.runner
+                                             'user]))]}))
+
+
+(def GAPhenotype
+  [:map
+   {:closed true}
+   [:id {:optional true} :uuid]
+   [:sym some?]
+   [:expr {:optional true} any?]
+   [:score {:optional true} number?]
+   [:util {:optional true} any?]
+   [:last-op {:optional true} :string]
+   [:mods-applied {:optional true} :int]])
+
+
+(def GAPopulationPhenotypes
+  [:vector #'GAPhenotype])
+
+
+(def GAMutation
+  [:map
+   {:closed true}
+   [:op :keyword]
+   [:label {:optional true} :string]
+   [:leaf-modifier-fn {:optional true} fn?]
+   [:modifier-fn {:optional true} fn?]
+   [:find-expr {:optional true} some?]
+   [:replace-expr {:optional true} some?]])
+
+
+(def SolverRunConfig
+  [:map
+   {:closed true}
+   [:iters pos-int?]
+   [:initial-phenos #'GAPopulationPhenotypes]
+   [:initial-muts [:sequential #'GAMutation]]
+   [:use-gui? :boolean]
+   [:max-leafs pos-int?]
+   [:input-phenos-count {:optional true} pos-int?]
+   [:log-steps pos-int?]
+   [:use-flamechart [:maybe :boolean]]
+   [:input-xs-exprs [:sequential some?]]
+   [:input-ys-exprs [:sequential some?]]])
+
+
+(def SolverRunArgs
+  [:map
+   {:closed true}
+   [:sim->gui-chan {:optional true} some?]
+   [:sim-stop-start-chan {:optional true} some?]
+   [:extended-domain-args map?]
+   [:input-xs-list some?]
+   [:input-xs-count pos-int?]
+   [:input-xs-vec [:vector double?]]
+   [:input-ys-vec [:vector double?]]
+   [:input-iters pos-int?]
+   [:initial-phenos [:maybe [:sequential map?]]]
+   [:input-phenos-count [:maybe pos-int?]]
+   [:max-leafs [:maybe pos-int?]]])
+
+
+(def SolverEvalArgs
+  [:map
+   {:closed false}
+   [:input-xs-list some?]
+   [:input-xs-count pos-int?]])
+
+
+(def SolverRunResults
+  [:map
+   {:closed true}
+   [:iters-done number?]
+   [:final-population map?]
+   [:next-step :keyword]])
diff --git a/test/closyr/ops_common_test.clj b/test/closyr/ops_common_test.clj
index 4a5ce37..fae2364 100644
--- a/test/closyr/ops_common_test.clj
+++ b/test/closyr/ops_common_test.clj
@@ -98,6 +98,19 @@
                    {"1/5+Sin(ArcSin(x))" 1}))))))))
 
 
+(deftest simplify-with-ignore-presets
+  (testing "simplify ignore"
+    (reset! ops-common/do-not-simplify-fns* {"x" 1})
+    (let [x (F/Dummy "x")]
+      (is (= (update (ops-common/maybe-simplify {:expr x})
+                     :expr str)
+             {:expr    "x"
+              :simple? true}))
+      (is (= @ops-common/do-not-simplify-fns*
+             {"x" 2})))
+    (reset! ops-common/do-not-simplify-fns* {})))
+
+
 (deftest simplify-test
   (testing "simplify trig compose"
     (let [x (F/Dummy "x")]
@@ -113,7 +126,7 @@
       (fn []
         (let [x (F/Dummy "x")]
           (is (= (dissoc (update (ops-common/maybe-simplify {:expr (F/Log (F/ArcSin x)) :util (ops-common/new-util)})
-                         :expr str)
+                                 :expr str)
                          :util)
                  {:expr    "Log(ArcSin(x))"
                   :simple? true}))))))
@@ -132,17 +145,6 @@
                        :expr str))
              {:expr "1+Sqrt(x)+Cos(x)+Sin(x)+2*(Cos(ArcSin(x))+Tan(ArcSin(x)))"}))))
 
-  (testing "simplify ignore"
-    (reset! ops-common/do-not-simplify-fns* {"x" 1})
-    (let [x (F/Dummy "x")]
-      (is (= (update (ops-common/maybe-simplify {:expr x})
-                     :expr str)
-             {:expr    "x"
-              :simple? true}))
-      (is (= @ops-common/do-not-simplify-fns*
-             {"x" 2})))
-    (reset! ops-common/do-not-simplify-fns* {}))
-
   (testing "simplify sum"
     (let [x (F/Dummy "x")]
       (is (= (binding [ops-common/*simplify-max-leafs* 100]
diff --git a/test/closyr/ops_modify_test.clj b/test/closyr/ops_modify_test.clj
index f48108f..4431b86 100644
--- a/test/closyr/ops_modify_test.clj
+++ b/test/closyr/ops_modify_test.clj
@@ -2,7 +2,7 @@
   (:require
     [clojure.core.async :as async :refer [go go-loop timeout <!! >!! <! >! chan put! take! alts!! alt!! close!]]
     [clojure.test :refer :all]
-    [closyr.dataset.prng :as prng]
+    [closyr.util.prng :as prng]
     [closyr.ops.common :as ops-common]
     [closyr.ops.initialize :as ops-init]
     [closyr.ops.modify :as ops-modify])
diff --git a/test/closyr/ops_test.clj b/test/closyr/ops_test.clj
index 8e926a8..5b4b278 100644
--- a/test/closyr/ops_test.clj
+++ b/test/closyr/ops_test.clj
@@ -1,7 +1,7 @@
 (ns closyr.ops-test
   (:require
     [clojure.test :refer :all]
-    [closyr.dataset.prng :as prng]
+    [closyr.util.prng :as prng]
     [closyr.ops :as ops]
     [closyr.ops.common :as ops-common]
     [closyr.ops.eval :as ops-eval]
diff --git a/test/closyr/symbolic_regression_test.clj b/test/closyr/symbolic_regression_test.clj
index 02a1ecb..8814eb4 100644
--- a/test/closyr/symbolic_regression_test.clj
+++ b/test/closyr/symbolic_regression_test.clj
@@ -35,7 +35,9 @@
                                  (reset! args*
                                          [(dissoc run-config :initial-muts :initial-phenos :input-xs-exprs :input-ys-exprs)
                                           (dissoc run-args :extended-domain-args :initial-phenos :input-xs-list)])
-                                 {:next-step :stop})
+                                 {:iters-done       123
+                                  :final-population {}
+                                  :next-step        :stop})
                                #'symreg/config->log-steps (fn [_ _] 200)}
                 (fn []
                   (symreg/run-app-from-cli-args
@@ -46,7 +48,9 @@
                      :ys             [1 4 19]
                      :use-flamechart true
                      :max-leafs      20})))
-              {:next-step :stop}))
+              {:iters-done       123
+               :final-population {}
+               :next-step        :stop}))
 
         (is (= @args*
                [{:iters          20
@@ -71,14 +75,18 @@
                                  (reset! args*
                                          [(dissoc run-config :initial-muts :initial-phenos :input-xs-exprs :input-ys-exprs)
                                           (dissoc run-args :extended-domain-args :initial-phenos :input-xs-list)])
-                                 {:next-step :stop})
+                                 {:iters-done       123
+                                  :final-population {}
+                                  :next-step        :stop})
                                #'symreg/config->log-steps (fn [_ _] 200)}
                 (fn []
                   (symreg/run-app-from-cli-args
                     {:population 30
                      :iterations 20
                      :headless   true})))
-              {:next-step :stop}))
+              {:iters-done       123
+               :final-population {}
+               :next-step        :stop}))
 
         (is (= @args*
                [{:iters          20
diff --git a/test/closyr/dataset_prng_test.clj b/test/closyr/util_prng_test.clj
similarity index 91%
rename from test/closyr/dataset_prng_test.clj
rename to test/closyr/util_prng_test.clj
index f6a1bd2..05b767d 100644
--- a/test/closyr/dataset_prng_test.clj
+++ b/test/closyr/util_prng_test.clj
@@ -1,7 +1,7 @@
-(ns closyr.dataset-prng-test
+(ns closyr.util-prng-test
   (:require
     [clojure.test :refer :all]
-    [closyr.dataset.prng :as prng]))
+    [closyr.util.prng :as prng]))
 
 
 (defn- test-rand-int-gen
diff --git a/test/closyr/util_spec_test.clj b/test/closyr/util_spec_test.clj
new file mode 100644
index 0000000..be18e74
--- /dev/null
+++ b/test/closyr/util_spec_test.clj
@@ -0,0 +1,89 @@
+(ns closyr.util-spec-test
+  (:require
+    [clojure.pprint :as pp]
+    [clojure.test :refer :all]
+    [closyr.util.spec :as specs]
+    [malli.core :as m]
+    [malli.instrument :as mi]))
+
+
+(deftest defined-schemas
+  (testing "GAPhenotype failure case"
+    (is (thrown? Exception
+          (specs/validate!
+            "test-pheno"
+            #'specs/GAPhenotype
+            {}))))
+
+  (testing "GAMutation failure case"
+    (is (thrown? Exception
+          (specs/validate!
+            "test-mutation"
+            #'specs/GAMutation
+            {}))))
+
+  (testing "GAPopulation failure case"
+    (is (thrown? Exception
+          (specs/validate!
+            "test-pop"
+            #'specs/GAPopulationPhenotypes
+            {}))))
+
+
+  (testing "SolverRunConfig failure case"
+    (is (thrown? Exception
+          (specs/validate!
+            "test-solver-run-config"
+            #'specs/SolverRunConfig
+            {}))))
+
+  (testing "SolverRunArgs failure case"
+    (is (thrown? Exception
+          (specs/validate!
+            "test-solver-run-args"
+            #'specs/SolverRunArgs
+            {}))))
+
+  (testing "SolverRunResults failure case"
+    (is (thrown? Exception
+          (specs/validate!
+            "test-solver-run-results"
+            #'specs/SolverRunResults
+            {})))))
+
+
+(deftest check-instrumented
+  (testing "All default defns"
+    (do
+      (require 'closyr.symbolic-regression)
+      (let [ss (m/function-schemas)]
+        (is (=
+              (count ss)
+              ;; the number of ns which contain defns which have malli/schema metadata in entire src:
+              6))
+
+        (is (=
+              (reduce + 0 (map (fn [[k v]] (count v)) ss))
+              ;; the number of total defns which have malli/schema metadata in entire src:
+              10))))))
+
+
+#_(deftest check-can-uninstrument
+    (testing "Can de-instrument"
+      (let [_ (#'specs/disable-validate-instrumentation!)]
+        (mi/unstrument!)
+
+
+
+        (is (= (specs/validate!
+                 "test-solver-run-results"
+                 #'specs/SolverRunResults
+                 {})
+               true))
+
+        (is (= (#'ops/compute-residual nil nil)
+               ops/max-resid))
+
+
+        (is (= (ops-common/extend-xs [0.1 "a"])
+               [])))))