diff --git a/servo/src/test/content/harness.js b/servo/src/test/content/harness.js
index 76540b2a1a59..48c41d214b1e 100644
--- a/servo/src/test/content/harness.js
+++ b/servo/src/test/content/harness.js
@@ -20,8 +20,8 @@ function _printer(opstr, op) {
   };
 }
 
-var is          = _printer("==",           function (a,b) { return a == b; });
-var is_not      = _printer("!=",           function (a,b) { return a != b; });
+var is          = _printer("===",          function (a,b) { return a === b; });
+var is_not      = _printer("!==",          function (a,b) { return a !== b; });
 var is_a        = _printer("is a",         function (a,b) { return a instanceof b; });
 var is_not_a    = _printer("is not a",     function (a,b) { return !(a instanceof b); });
 var is_in       = _printer("is in",        function (a,b) { return a in b; });
diff --git a/servo/src/test/content/test_collections.html b/servo/src/test/content/test_collections.html
index 0c0f9aa04aaf..61cf77ed61f7 100644
--- a/servo/src/test/content/test_collections.html
+++ b/servo/src/test/content/test_collections.html
@@ -9,7 +9,7 @@
 function check_collection(obj, num, classes, name) {
     is_a(obj, HTMLCollection);
     is(obj.length, num);
-    is(obj[obj.length], null);
+    is(obj[obj.length], undefined);
 
     if (classes === undefined)
         return;
@@ -17,7 +17,7 @@ function check_collection(obj, num, classes, name) {
     classes = [Element, HTMLElement].concat(classes);
 
     for (var i=0; i<obj.length; i++) {
-        is_not(obj[i], null);
+        is_not(obj[i], undefined);
         is(obj[i].tagName, name);
         for (var j=0; j<classes.length; j++) {
             is_a(obj[i], classes[j]);
diff --git a/servo/src/test/content/test_document_createElementNS.html b/servo/src/test/content/test_document_createElementNS.html
index 6ff35d4d6c1a..68b0447639ff 100644
--- a/servo/src/test/content/test_document_createElementNS.html
+++ b/servo/src/test/content/test_document_createElementNS.html
@@ -20,11 +20,11 @@
             }
             // test2: Node.namespaceURI
             {
-                is(document.namespaceURI, null, "test2.0: createElementNS");
+                is(document.namespaceURI, undefined, "test2.0: createElementNS");
                 is(document.documentElement.namespaceURI, "http://www.w3.org/1999/xhtml", "test2.1: createElementNS");
                 var scriptElt = document.getElementById("script");
-                is(scriptElt.firstChild.namespaceURI, null, "test2.2: createElementNS");
-                is(scriptElt.nextSibling.namespaceURI, null, "test2.3: createElementNS");
+                is(scriptElt.firstChild.namespaceURI, undefined, "test2.2: createElementNS");
+                is(scriptElt.nextSibling.namespaceURI, undefined, "test2.3: createElementNS");
             }
 
             finish();