rspec users - Apr 2011 - Routing assertions

Hi

Thanks for help me out

 I have two routes :
       match ''admin/categories'' =>
''admin#categories'', :as =>
''admin_category''
       match ''admin/categories/:sub_category'' =>
''admin#categories''

In rspec

------------------------------------------------------------------------------------------------------------------------------------------------------
      For first route

        assert_routing({:path => "admin/categories"}, {:controller
=>
''admin'', :action => ''categories''})

      For second route

         assert_recognizes({:controller=>''admin'', :action
=>
''categories'', :sub_category=>''2''},
''admin/categories/2'')
-----------------------------------------------------------------------------------------------------------------------------------------------------------
  For second route if i am using assert_routing  method I am getting
below error

        Failure/Error: assert_routing({:path =>
"admin/categories/2"},
{:controller => ''admin'', :action =>
''categories'', :sub_category =>
''2''})
     Test::Unit::AssertionFailedError:
       found extras <{:sub_category=>"2"}>, not <{}>

  Why assert_routing method is failing for second route? And also let
me know I which scenarios should I use assert_routing,
assert_generates and assert_recognizes?