diff --git a/tests/PartialApplicationTest.php b/tests/PartialApplicationTest.php
index 6bed981..d29c63e 100644
--- a/tests/PartialApplicationTest.php
+++ b/tests/PartialApplicationTest.php
@@ -84,4 +84,22 @@ class PartialApplicationTest extends \PHPUnit\Framework\TestCase
 
         $applied(1);
     }
+
+    public function testYCombinatorFactorial()
+    {
+        $applied = f\fix(function ($f) {
+            return function ($x) use ($f) { return $x >= 2 ? $f($x-1) * $x : 1; };
+        });
+
+        $this->assertEquals(6, $applied(3));
+        $this->assertEquals(24, $applied(4));
+    }
+
+    public function testYCombinatorCurried()
+    {
+        $applied = f\fix(f\curry(function ($f, $x) { return $x >= 2 ? $f($x-1) * $x : 1; }));
+
+        $this->assertEquals(6,  $applied(3));
+        $this->assertEquals(24, $applied(4));
+    }
 }
\ No newline at end of file