added Casper#exists() method to check for a DOM element

@@ -306,6 +306,20 @@
         },
 
         /**
+         * Checks if an element matching the provided CSS3 selector exists in
+         * current page DOM.
+         *
+         * @return Boolean
+         */
+        exists: function(selector) {
+            return self.evaluate(function() {
+                return __utils__.exists('%selector%');
+            }, {
+                selector: selector
+            });
+        };
+
+        /**
          * Fills a form with provided field values.
          *
          * @param  String  selector  A CSS3 selector to the target form to fill

@@ -41,6 +41,10 @@ phantom.Casper.extend({
         return this.assert(pattern.test(subject), message);
     },
 
+    assertSelectorExists: function(selector, message) {
+        return this.assert(this.exists(selector), message);
+    },
+
     assertTitle: function(expected, message) {
         return this.assertEvalEquals(function() {
             return document.title;