Correct method, tests and documentation

@@ -450,14 +450,19 @@ Asserts that the provided input is of the given type::
 ``assertInstanceOf()``
 -------------------------------------------------------------------------------
 
-**Signature:** ``assertInstanceOf(mixed input, String className[, String message])``
+**Signature:** ``assertInstanceOf(mixed input, function constructor[, String message])``
 
 Asserts that the provided input is of the given className::
-
+    
+    function Cow() {
+        this.moo = function moo() {
+            return 'moo!';
+        };
+    } 
     casper.test.begin('assertInstanceOf() tests', 1, function suite(test) {
-        var daisy = new Cow(){};
-        test.assertInstanceOf(daisy, "Cow", "Okay, daisy is a cow.");
-        test.assertInstanceOf(daisy, "Casper", "Moo is not Boo");
+        var daisy = new Cow();
+        test.assertInstanceOf(daisy, Cow, "Okay, daisy is a cow.");
+        test.assertInstanceOf(daisy, Casper, "Moo is not Boo");
         test.done();
     });
 

@@ -842,20 +842,20 @@ Tester.prototype.assertType = function assertType(subject, type, message) {
 /**
  * Asserts that the provided subject is of the given class name.
  *
- * @param  mixed   subject    The value to test
- * @param  String  className  The javascript class name
- * @param  String  message    Test description
- * @return Object             An assertion result object
+ * @param  mixed   subject          The value to test
+ * @param  function  constructor    The object constructor
+ * @param  String  message          Test description
+ * @return Object                   An assertion result object
  */
-Tester.prototype.assertInstanceOf = function assertInstanceOf(subject, className, message) {
+Tester.prototype.assertInstanceOf = function assertInstanceOf(subject, constructor, message) {
     "use strict";
-    var actual = subject instanceof className;
+    var actual = subject instanceof constructor;
     return this.assert(utils.equals(actual, true), message, {
         type: "assertInstanceOf",
-        standard: f('Subject is an instance of: "%s"', className),
+        standard: f('Subject is an instance of: "%s"', constructor),
         values: {
             subject: subject,
-            className: className,
+            constructor: constructor,
             actual: actual
         }
     });

@@ -2,7 +2,7 @@
 /*jshint strict:false, maxstatements:99*/
 var fs = require('fs');
 
-casper.test.begin('Common assertions tests', 45, function(test) {
+casper.test.begin('Common assertions tests', 46, function(test) {
     casper.start('tests/site/index.html', function() {
         test.assertTextExists('form', 'Tester.assertTextExists() checks that page body contains text');
         test.assertTextExist('form', 'Tester.assertTextExist() checks that page body contains text [alias]');
@@ -60,7 +60,9 @@ casper.test.begin('Common assertions tests', 45, function(test) {
         test.assertTitleMatch(/test index/, 'Tester.assertTitleMatch() works as expected');
         test.assertTitleMatches(/test index/, 'Tester.assertTitleMatches() works as expected [alias]');
         test.assertType("plop", "string", "Tester.assertType() works as expected");
-        test.assertInstanceOf(casper, "Casper", "Tester.assertInstanceOf() works as expected");
+        // we need a constructor and an object
+        function Cow(){}; var daisy = new Cow();
+        test.assertInstanceOf(daisy, Cow, "Tester.assertInstanceOf() works as expected");
         test.assertUrlMatch(/index\.html$/, "Tester.assertUrlMatch() works as expected");
         test.assertUrlMatches(/index\.html$/, "Tester.assertUrlMatches() works as expected [alias]");
         test.assertVisible('img', 'Tester.assertVisible() works as expected');