diff --git a/src/propeller/gp.cljc b/src/propeller/gp.cljc
index 47d8d82..2a3eaff 100755
--- a/src/propeller/gp.cljc
+++ b/src/propeller/gp.cljc
@@ -52,16 +52,18 @@
       (let [evaluated-pop (sort-by :total-error
                                    (#?(:clj  pmap
                                        :cljs map)
-                                     (partial error-function argmap) population))
+                                     (partial error-function argmap (:training-data argmap))
+                                     population))
             best-individual (first evaluated-pop)]
         (report evaluated-pop generation argmap)
         (cond
           ;; Success on training cases is verified on testing cases
           (zero? (:total-error best-individual))
           (do (prn {:success-generation generation})
-              (prn {:total-test-error (:total-error (error-function argmap best-individual :test))})
-              (#?(:clj shutdown-agents))
-              )
+              (prn {:total-test-error (:total-error (error-function argmap
+                                                                    (:testing-data argmap)
+                                                                    best-individual))})
+              (#?(:clj shutdown-agents)))
           ;;
           (>= generation max-generations)
           nil
diff --git a/src/propeller/problems/simple_regression.cljc b/src/propeller/problems/simple_regression.cljc
index cd56a97..8b75f7b 100755
--- a/src/propeller/problems/simple_regression.cljc
+++ b/src/propeller/problems/simple_regression.cljc
@@ -4,21 +4,21 @@
             [propeller.push.state :as state]
             [propeller.tools.math :as math]))
 
-;; =============================================================================
-;; Problem: f(x) = 7x^2 - 20x + 13
-;; =============================================================================
-
-(defn- target-function-hard
-  "Target function: f(x) = 7x^2 - 20x + 13"
-  [x]
-  (+ (* 7 x x) (* -20 x) 13))
-
 (defn- target-function
   "Target function: f(x) = x^3 + x + 3"
   [x]
   (+ (* x x x) x 3))
 
-; Set of original propel instructions
+(def training-data
+  (let [training-inputs (range -10 11)]
+    {:inputs  training-inputs
+     :outputs (map target-function training-inputs)}))
+
+(def testing-data
+  (let [testing-inputs (concat (range -20 -10) (range 11 21))]
+    {:inputs  testing-inputs
+     :outputs (map target-function testing-inputs)}))
+
 (def instructions
   (list :in1
         :integer_add
@@ -32,25 +32,13 @@
         0
         1))
 
-(defn train-and-test-data
-  [target-function]
-  (let [train-inputs (range -10 11)
-        test-inputs (concat (range -20 -10) (range 11 21))]
-    {:train {:inputs  train-inputs
-             :outputs (map target-function train-inputs)}
-     :test  {:inputs  test-inputs
-             :outputs (map target-function test-inputs)}}))
-
 (defn error-function
   "Finds the behaviors and errors of an individual. The error is the absolute
   deviation between the target output value and the program's selected behavior,
   or 1000000 if no behavior is produced. The behavior is here defined as the
   final top item on the INTEGER stack."
-  ([argmap individual]
-   (error-function argmap individual :train))
-  ([argmap individual subset]
+  ([argmap data individual]
    (let [program (genome/plushy->push (:plushy individual) argmap)
-         data (get (train-and-test-data target-function) subset)
          inputs (:inputs data)
          correct-outputs (:outputs data)
          outputs (map (fn [input]
@@ -75,4 +63,6 @@
 
 (def arglist
   {:instructions instructions
-   :error-function error-function})
\ No newline at end of file
+   :error-function error-function
+   :training-data training-data
+   :testing-data testing-data})
\ No newline at end of file