I've written a custom controller that exploits the StandardSetController class to return a page of records and allow pagination.

VF controller has three (relevant) methods:

getPage()  - returns List of records in current pageset (pagesize = 10)

previousPage() - executes the previous() method on the standard set controlller object

nextPage() - executes the next() method on the standard set controller object

The StandardSetController is constructed using a Database.getQueryLocator per the doc

setCtlr = new ApexPages.StandardSetController(

Database.getQueryLocator(

[Select id, name, Account__r.name from Foo__c where id in :fooIdSet]));

When I set up my APEX test method:

1.  Insert 11 rows into database  //works ok

2.  Assert that getPage() returns 10 rows  // assertion passes

3.  Execute nextPage() on the controller

4.  Assert that getPage() returns 1 row (the 11th)

Here's the problem: step #3 fails because VF comes back with:

System.VisualforceException: Modified rows exist in the records collection!

I checked the creation datetime and lastmodify datetime just prior to executing Step3 and all is OK, the records haven't mysteriously been changed underneath.

I get the same error (in a non-Sites test whilst logged in as admin and simply executing the VF page in the browser.

What would cause this error?