Is the testing a bit too light on GROUP BY DISTINCT?

In [1], Yaoguang reported an Assert failure in expand_grouping_sets.
Since beta2 deadline is looming, I pushed a quick fix for that.

As mentioned over on bugs, only 1 test triggers that code and because
the List of IntLists always had an empty list as the first element due
to the code just above sorting the top-level List by the number of
elements each of the contained IntLists, the NIL was always at the
start of the top-level List.

It wasn't too hard to modify the test to change that.

I wonder if the testing for the feature is just a bit too light.

Would it maybe be worth adding a GROUP BY DISTINCT with GROUPING SETS test?

Any thoughts?

David

[1] https://www.postgresql.org/message-id/17067-665d50fa321f79e0@postgresql.org