diff --git a/lib/ace/test/mockdom.js b/lib/ace/test/mockdom.js
index 2d0128e040a..7158f7cac0e 100644
--- a/lib/ace/test/mockdom.js
+++ b/lib/ace/test/mockdom.js
@@ -165,6 +165,9 @@ function Node(name) {
         
         return node;
     };
+    this.before = function(node) {
+        if (this.parentNode) this.parentNode.insertBefore(node, this);
+    };
     this.hasChildNodes = function() {
         return this.childNodes.length > 0;
     };