Small changes. Generally, prefer find-x-for to reinventing the wheel.

src/arboretum/dengine/dengine.clj

@@ -1,12 +1,10 @@
 (ns arboretum.dengine.dengine
   (:require
    [arboretum.dengine.kb :refer [!kb find-case-for find-feature-for remember!]]
-   [arboretum.dengine.protocols :refer [Case]]
    [taoensso.telemere :refer [log!]]))
 
-
 (defn dengine [feat c]
-  (let [c' (if (satisfies? Case c) c (-> @!kb :cases c))
+  (let [c' (find-case-for @!kb c)
         f' (find-feature-for @!kb feat)]
     (log! {:msg (format "Inferring value of `%s` for `%s`"
                  (:case-id c') (:feature-id f'))})

test/dengine/dengine_test.clj

@@ -7,6 +7,7 @@
       (testing "Context of the test assertions"
         (let [expected true
               actual (:value
-                      (decide-feat :is-entitled-to-widows-allowance :case-1))](is (= actual expected)))))  
+                      (decide-feat :is-entitled-to-widows-allowance :case-1))]
+          (is (= actual expected)))))