diff --git a/tests/wpt/mozilla/tests/mozilla/characterdata.html b/tests/wpt/mozilla/tests/mozilla/characterdata.html
index f4f586e9aec..22b7aa3c65d 100644
--- a/tests/wpt/mozilla/tests/mozilla/characterdata.html
+++ b/tests/wpt/mozilla/tests/mozilla/characterdata.html
@@ -9,14 +9,7 @@
   <script>
   test(function() {
     var a = document.getElementsByTagName('p')[0].childNodes[0];
-    a.data = "This is the character data, append more 資料，測試資料";
-
-    // insert test non-utf8
-    a.insertData(26, " test");
-    assert_equals(a.data, "This is the character data test, append more 資料，測試資料");
-    // insert test utf8
-    a.insertData(48, "更多");
-    assert_equals(a.data, "This is the character data test, append more 資料，更多測試資料");
+    a.data = "This is the character data test, append more 資料，更多測試資料";
 
     // delete test non-utf8
     a.deleteData(40, 5);
diff --git a/tests/wpt/web-platform-tests/dom/nodes/CharacterData-insertData.html b/tests/wpt/web-platform-tests/dom/nodes/CharacterData-insertData.html
index 5bcd6b10cef..6e907f5437d 100644
--- a/tests/wpt/web-platform-tests/dom/nodes/CharacterData-insertData.html
+++ b/tests/wpt/web-platform-tests/dom/nodes/CharacterData-insertData.html
@@ -31,6 +31,16 @@ function testNode(create, type) {
     node.insertData(4, "ing")
     assert_equals(node.data, "testing")
   }, type + ".insertData() at the end")
+
+  test(function() {
+    var node = create()
+    node.data = "This is the character data, append more 資料，測試資料";
+
+    node.insertData(26, " test");
+    assert_equals(node.data, "This is the character data test, append more 資料，測試資料");
+    node.insertData(48, "更多");
+    assert_equals(node.data, "This is the character data test, append more 資料，更多測試資料");
+  }, type + ".insertData() with non-ascii data")
 }
 
 testNode(function() { return document.createTextNode("test") }, "Text")