diff --git a/src/recursion.clj b/src/recursion.clj
index 44d39e9..5bbd715 100644
--- a/src/recursion.clj
+++ b/src/recursion.clj
@@ -3,6 +3,9 @@
 (defn product [coll]
   :-)
 
+(defn singleton? [coll]
+  :-)
+
 (defn last-element [coll]
   :-)
 
diff --git a/test/recursion_test.clj b/test/recursion_test.clj
index eb6b54b..26355a1 100644
--- a/test/recursion_test.clj
+++ b/test/recursion_test.clj
@@ -9,6 +9,12 @@
   (product [0 1 2])   => 0
   (product #{2 3 4})  => 24)
 
+(facts "singleton?"
+       (singleton? [1])     => true
+       (singleton? #{2})    => true
+       (singleton? [])      => false
+       (singleton? [1 2 3]) => false)
+
 (facts "last-element"
   (last-element [])      => nil
   (last-element [1 2 3]) => 3