diff --git a/test/util.js b/test/util.js
new file mode 100644
index 0000000..f76b5a5
--- /dev/null
+++ b/test/util.js
@@ -0,0 +1,33 @@
+var util = require('../src/util.js')
+var assert = require('assert')
+
+describe('util', function() {
+
+  describe('byte array and word array conversions', function(){
+    var bytes, wordArray;
+
+    beforeEach(function(){
+      bytes = [
+        98, 233, 7, 177, 92, 191, 39, 213, 66, 83,
+        153, 235, 246, 240, 251, 80, 235, 184, 143, 24
+      ]
+      wordArray = {
+        words: [1659439025, 1556031445, 1112775147, -151979184, -340226280],
+        sigBytes: 20
+      }
+    })
+
+    describe('bytesToWords', function() {
+      it('works', function() {
+        assert.deepEqual(util.bytesToWordArray(bytes), wordArray)
+      })
+    })
+
+    describe('bytesToWords', function() {
+      it('works', function() {
+        assert.deepEqual(util.wordArrayToBytes(wordArray), bytes)
+      })
+    })
+  })
+
+})