diff --git a/src/wanijo/instance/domain.clj b/src/wanijo/instance/domain.clj
index f1ac656..95b9e09 100644
--- a/src/wanijo/instance/domain.clj
+++ b/src/wanijo/instance/domain.clj
@@ -1,6 +1,5 @@
 (ns wanijo.instance.domain
   (:require [clojure.spec.alpha :as spec]
-            [clojure.spec.test.alpha :as spectest]
             [wanijo.framework.neo4j :as neo4j]
             [clojure.pprint :as pprint]))
 
@@ -109,7 +108,19 @@
    ON MATCH SET p.updated_at = {now},
                 p.value = {value}")
 
+(spec/def ::now ::neo4j/date-str)
+(spec/def ::prop-tuple-values
+  (spec/keys :req-un [::neo4j/uuid
+                      ::now
+                      ::value
+                      ::instance_uuid
+                      ::attribute_uuid]))
+(spec/def ::prop-tuple
+  (spec/coll-of
+   (spec/tuple fn? ::prop-tuple-values)))
+
 (defn instance->prop-tuples [instance]
+  {:post [(spec/assert ::prop-tuple %)]}
   (map (fn [prop]
          (let [prop-uuid (:uuid prop)
                uuid (if (empty? prop-uuid)
@@ -123,18 +134,6 @@
              :attribute_uuid (-> prop :attribute :uuid)}]))
        (:properties instance)))
 
-(spec/def ::prop-tuple-values
-  (spec/keys :req-un [::neo4j/uuid
-                      ::neo4j/date-str
-                      ::value
-                      ::instance_uuid
-                      ::attribute_uuid]))
-(spec/def ::prop-tuple
-  (spec/tuple fn? ::prop-tuple-values))
-(spec/fdef instance->prop-tuples
-  :ret (spec/coll-of ::prop-tuple))
-(spectest/instrument `instance->prop-tuples)
-
 (defn edit! [instance]
   (let [prop-tuples (instance->prop-tuples instance)]
     (apply neo4j/exec-queries!
diff --git a/src/wanijo/main.clj b/src/wanijo/main.clj
index 3a3a212..254a548 100644
--- a/src/wanijo/main.clj
+++ b/src/wanijo/main.clj
@@ -3,6 +3,8 @@
             [wanijo.handler :as wanijo])
   (:gen-class))
 
+(spec/check-asserts true)
+
 (defonce server (atom nil))
 
 (defn start-server!