Ordering Error

Hi all

Searched the docs, archives etc. but can't find any reference to this
problem I'm having with ORDER BY used in conjunction with SELECT...AS.

A simplified demonstration:

radius=# SELECT col1 AS testing FROM test ORDER BY testing ASC;
  testing
----------
  Ordering
  Test
  This
  an
  is
(5 rows)

But I need the lowercased ordering result for this column for a
case-insensitivity listing, however I get

radius=# SELECT col1 AS testing FROM test ORDER BY lower(testing) ASC;
ERROR:  Attribute "testing" not found

Using the ordinal notation (ie. ORDER BY lower(1) ASC) gives weird results
(in my original query).

I can't use ORDER BY lower(col1) in my original and more complex query as
the column is the result of a function.

What obviousness would I be missing here?

version = 7.3.2

cheers
Jason