Rails - Jul 2005 - weird test problem

So, I can run all my unit tests fine if I run them directly (i.e.
''ruby test/unit/restaurant.rb'').

But, when I use rake, I get errors like these:

  2) Error:
test_truth(RestaurantTest):
NameError: uninitialized constant Restaurant
   
/home/joe/joe/sites/my_site/trunk/config/..//vendor/rails/activesupport/lib/active_support/dependencies.rb:186:in
`const_missing''
    ./test/unit/restaurant_test.rb:7:in `setup_without_fixtures''
    

Why would that be?