diff --git a/js/tests/unit/modal.js b/js/tests/unit/modal.js
index 1762904803..9b7fb0aa66 100644
--- a/js/tests/unit/modal.js
+++ b/js/tests/unit/modal.js
@@ -669,7 +669,7 @@ $(function () {
   })
 
   QUnit.test('transition duration should be the modal-dialog duration before triggering shown event', function (assert) {
-    assert.expect(2)
+    assert.expect(1)
     var done = assert.async()
     var style = [
       '<style>',
@@ -694,22 +694,17 @@ $(function () {
       '</div>'
     ].join('')
 
-    var beginTimestamp = 0
     var $modal = $(modalHTML).appendTo('#qunit-fixture')
-    var $modalDialog = $('.modal-dialog')
-    var transitionDuration  = Util.getTransitionDurationFromElement($modalDialog[0])
-
-    assert.strictEqual(transitionDuration, 300)
+    var expectedTransitionDuration = 300
+    var spy = sinon.spy(Util, 'getTransitionDurationFromElement')
 
     $modal.on('shown.bs.modal', function () {
-      var diff = Date.now() - beginTimestamp
-      assert.ok(diff < 400)
+      assert.ok(spy.returned(expectedTransitionDuration))
       $style.remove()
+      spy.restore()
       done()
     })
       .bootstrapModal('show')
-
-    beginTimestamp = Date.now()
   })
 
   QUnit.test('should dispose modal', function (assert) {