diff --git a/challenges/01-front-end-development-certification/intermediate-bonfires.json b/challenges/01-front-end-development-certification/intermediate-bonfires.json
index 22ba611354..59cd3ed5db 100644
--- a/challenges/01-front-end-development-certification/intermediate-bonfires.json
+++ b/challenges/01-front-end-development-certification/intermediate-bonfires.json
@@ -84,12 +84,19 @@
       "tests": [
         "assert(typeof diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]) === \"object\", 'message: <code>diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5])</code> should return an array.');",
         "assert.sameMembers(diffArray([\"diorite\", \"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]), [\"pink wool\"], 'message: <code>[\"diorite\", \"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]</code> should return <code>[\"pink wool\"]</code>.');",
+        "assert(diffArray([\"diorite\", \"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]).length === 1, 'message: <code>[\"diorite\", \"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]</code> should return an array with one item.');",
         "assert.sameMembers(diffArray([\"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]), [\"diorite\", \"pink wool\"], 'message: <code>[\"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]</code> should return <code>[\"diorite\", \"pink wool\"]</code>.');",
+        "assert(diffArray([\"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]).length === 2, 'message: <code>[\"andesite\", \"grass\", \"dirt\", \"pink wool\", \"dead shrub\"], [\"diorite\", \"andesite\", \"grass\", \"dirt\", \"dead shrub\"]</code> should return an array with two items.');",
         "assert.sameMembers(diffArray([\"andesite\", \"grass\", \"dirt\", \"dead shrub\"], [\"andesite\", \"grass\", \"dirt\", \"dead shrub\"]), [], 'message: <code>[\"andesite\", \"grass\", \"dirt\", \"dead shrub\"], [\"andesite\", \"grass\", \"dirt\", \"dead shrub\"]</code> should return <code>[]</code>.');",
+        "assert(diffArray([\"andesite\", \"grass\", \"dirt\", \"dead shrub\"], [\"andesite\", \"grass\", \"dirt\", \"dead shrub\"]).length === 0, 'message: <code>[\"andesite\", \"grass\", \"dirt\", \"dead shrub\"], [\"andesite\", \"grass\", \"dirt\", \"dead shrub\"]</code> should return an empty array.');",
         "assert.sameMembers(diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]), [4], 'message: <code>[1, 2, 3, 5], [1, 2, 3, 4, 5]</code> should return <code>[4]</code>.');",
+        "assert(diffArray([1, 2, 3, 5], [1, 2, 3, 4, 5]).length  === 1, 'message: <code>[1, 2, 3, 5], [1, 2, 3, 4, 5]</code> should return an array with one item.');",
         "assert.sameMembers(diffArray([1, \"calf\", 3, \"piglet\"], [1, \"calf\", 3, 4]), [\"piglet\", 4], 'message: <code>[1, \"calf\", 3, \"piglet\"], [1, \"calf\", 3, 4]</code> should return <code>[\"piglet\", 4]</code>.');",
+        "assert(diffArray([1, \"calf\", 3, \"piglet\"], [1, \"calf\", 3, 4]).length === 2, 'message: <code>[1, \"calf\", 3, \"piglet\"], [1, \"calf\", 3, 4]</code> should return an array with two items.');",
         "assert.sameMembers(diffArray([], [\"snuffleupagus\", \"cookie monster\", \"elmo\"]), [\"snuffleupagus\", \"cookie monster\", \"elmo\"], 'message: <code>[], [\"snuffleupagus\", \"cookie monster\", \"elmo\"]</code> should return <code>[\"snuffleupagus\", \"cookie monster\", \"elmo\"]</code>.');",
-        "assert.sameMembers(diffArray([1, \"calf\", 3, \"piglet\"], [7, \"filly\"]), [1, \"calf\", 3, \"piglet\", 7, \"filly\"], 'message: <code>[1, \"calf\", 3, \"piglet\"], [7, \"filly\"]</code> should return <code>[1, \"calf\", 3, \"piglet\", 7, \"filly\"]</code>.');"
+        "assert(diffArray([], [\"snuffleupagus\", \"cookie monster\", \"elmo\"]).length === 3, 'message: <code>[], [\"snuffleupagus\", \"cookie monster\", \"elmo\"]</code> should return an array with three items.');",
+        "assert.sameMembers(diffArray([1, \"calf\", 3, \"piglet\"], [7, \"filly\"]), [1, \"calf\", 3, \"piglet\", 7, \"filly\"], 'message: <code>[1, \"calf\", 3, \"piglet\"], [7, \"filly\"]</code> should return <code>[1, \"calf\", 3, \"piglet\", 7, \"filly\"]</code>.');",
+        "assert(diffArray([1, \"calf\", 3, \"piglet\"], [7, \"filly\"]).length === 6, 'message: <code>[1, \"calf\", 3, \"piglet\"], [7, \"filly\"]</code> should return an array with six items.');"
       ],
       "type": "bonfire",
       "MDNlinks": [