diff --git a/project.clj b/project.clj
--- a/project.clj
+++ b/project.clj
@@ -6,7 +6,8 @@
   :dependencies [[org.clojure/clojure "1.8.0"]
                  [org.clojure/clojurescript "1.9.521"]
                  ; [andare "0.9.0"] 
-                  [org.clojure/core.async "0.4.474"]]
+                  [org.clojure/core.async "0.4.474"]
+                  [org.clojure/test.check "0.10.0-alpha3"]]
 
   :plugins [[lein-cljsbuild "1.1.5"]]
 
diff --git a/src/project_checkup/core.clj b/src/project_checkup/core.clj
--- a/src/project_checkup/core.clj
+++ b/src/project_checkup/core.clj
@@ -4,7 +4,11 @@
   (:require [clojure.java.shell :as shell]
             [clojure.string :as string])) 
 
-(defn get-extension [path] (re-find #"\.[a-zA-Z]+$" path))
+(defn get-extension [path] 
+  "Extracts the extension of a path.
+  Returns the extension with the period, e.g., '.txt' because that's the format 
+  people are used to seeing extensions in."
+  (re-find #"\.[a-zA-Z0-9]+$" path))
 
 (defn gather-project-info
   "Creates a dictionary of project information"
diff --git a/test/project_checkup/core_property_test.clj b/test/project_checkup/core_property_test.clj
new file mode 100644
--- /dev/null
+++ b/test/project_checkup/core_property_test.clj
@@ -0,0 +1,27 @@
+(ns project-checkup.core-property-test
+  (:gen-class)
+  (:require [clojure.test :refer :all]
+            [project-checkup.core :refer :all]
+            [clojure.test.check :as tc]
+            [clojure.test.check.generators :as gen]
+            [clojure.test.check.properties :as prop]
+            [clojure.test.check.clojure-test :refer :all]))
+
+
+;arguably redundant
+(defspec get-extension-returns-string 
+  100
+  (prop/for-all [st (gen/not-empty   gen/string-ascii)
+                 ext (gen/not-empty gen/string-alphanumeric) ]
+               (string? (get-extension (str st \. ext ))) ))
+
+
+(defspec get-extension-returns-extension 
+  100
+  (prop/for-all [st (gen/not-empty   gen/string-ascii)
+                 ext (gen/not-empty gen/string-alphanumeric) ]
+               (= (get-extension (str st \. ext )) 
+                  (str \. ext)) ))
+
+
+
diff --git a/test/project_checkup/core_test.clj b/test/project_checkup/core_test.clj
--- a/test/project_checkup/core_test.clj
+++ b/test/project_checkup/core_test.clj
@@ -39,6 +39,4 @@
     (is (= (get-extension "test.txt") ".txt"))
     (is (= (get-extension "./test.txt") ".txt"))
     (is (= (get-extension "test.txt.bak") ".bak"))
-    (is (= (get-extension ".hg/test.txt.bak") ".bak"))
-    )
-  )
+    (is (= (get-extension ".hg/test.txt.bak") ".bak"))))