diff --git a/shamwow_test.rb b/shamwow_test.rb
index 789f62c..4d37613 100644
--- a/shamwow_test.rb
+++ b/shamwow_test.rb
@@ -19,6 +19,7 @@ class TestShamwow < Test::Unit::TestCase
   end
 
   def test_sha2
+    assert_equal(Digest::SHA2.hexdigest(''), sha2(""))
     assert_equal(Digest::SHA2.hexdigest('abc'), sha2("abc"))
     assert_equal(Digest::SHA2.hexdigest("上一页"), sha2("上一页"))
     assert_equal(Digest::SHA2.hexdigest("😀"), sha2("😀"))