testing docs: fix notes about storing test failures

@@ -785,7 +785,7 @@ That will give something like this:
 
 .. note::
 
-    In CasperJS 1.1, you can store test successes by recording them listening to the tester ``pass`` event::
+    In CasperJS 1.1, you can store test failures by recording them listening to the tester ``fail`` event::
 
         var failures = [];