diff --git a/public/js/sorting/worker.js b/public/js/sorting/worker.js
index 58e7574..17b43cb 100644
--- a/public/js/sorting/worker.js
+++ b/public/js/sorting/worker.js
@@ -1,25 +1,27 @@
-function sleep(ms) {
-    var start = new Date().getTime();
-    while (new Date().getTime() - start < ms);
-}
+(function() {
+    function makeNumeric(array) {
+        var i;
+        for (i = 0; i < array.length; i++)
+            array[i] = parseInt(array[i]);
+    }
 
-function update(array) {
-    postMessage({"array": array, finished: false});
-    sleep(200);
-}
+    sleep = function(ms) {
+        var start = new Date().getTime();
+        while (new Date().getTime() - start < ms);
+    }
 
-function makeNumeric(array) {
-    var i;
-    for (i = 0; i < array.length; i++)
-        array[i] = parseInt(array[i]);
-}
+    update = function(array) {
+        postMessage({"array": array, finished: false});
+        sleep(200);
+    }
 
-onmessage = function(event) {
-    var array = event.data.array,
-        algorithm;
-    makeNumeric(array);
-    importScripts(event.data.file);
-    algorithm = eval(event.data.functionName);
-    algorithm(array);
-    postMessage({"array": array, finished: true});
-}
\ No newline at end of file
+    onmessage = function(event) {
+        var array = event.data.array,
+            algorithm;
+        makeNumeric(array);
+        importScripts(event.data.file);
+        algorithm = eval(event.data.functionName);
+        algorithm(array);
+        postMessage({"array": array, finished: true});
+    };
+})();
diff --git a/public/test/tests/sorting/worker.js b/public/test/tests/sorting/worker.js
index 4517f8b..0079dd7 100644
--- a/public/test/tests/sorting/worker.js
+++ b/public/test/tests/sorting/worker.js
@@ -22,8 +22,24 @@ test("update", 2, function() {
     postMessage.restore();
 });
 
-test("makeNumeric", 1, function() {
-    var array = ["1", "2", "3"];
-    makeNumeric(array);
-    deepEqual(array, [1, 2, 3]);
-});
\ No newline at end of file
+test("onmessage", 3, function() {
+    f = sinon.stub();
+    importScripts = sinon.stub();
+    sinon.stub(window, "postMessage");
+
+    onmessage({data: {
+        array: ["1", "2", "3"],
+        file: "f.js",
+        functionName: "f"
+    }});
+
+    ok(importScripts.calledWith("f.js"),
+       "The supplied JS file should be loaded.");
+    ok(f.calledWith([1, 2, 3]),
+       "The sort function should be called with the array.");
+    ok(postMessage.calledWith({array: [1, 2, 3], finished: true}),
+       "The worker should post a message with the result.");
+
+    f = importScripts = undefined;
+    postMessage.restore();
+});