So it turns out the at() method doesn’t quite do what I had initially thought….
I have recently been working on some tests for the new Newsletter extension for Mediawiki, specifically to test the NewslettterTablePager class. This thing extends the TablePager class in Mediawiki which is designed to make displaying information from a database table on a special page on a MediaWiki site easy, and also easily enable things such as sorting.
The code interacts with the database and gets a ResultWrapper object, and the Pager uses the numRows(), seek() and fetchObject() methods, all of which I thought would be incredibly simple to mock.