raise ArgumentError, not TypeError for an invalid etag strength

lib/sinatra/base.rb

@@ -288,8 +288,8 @@ module Sinatra
     # When the current request includes an 'If-None-Match' header with a
     # matching etag, execution is immediately halted. If the request method is
     # GET or HEAD, a '304 Not Modified' response is sent.
-    def etag(value, kind=:strong)
-      raise TypeError, ":strong or :weak expected" if ![:strong,:weak].include?(kind)
+    def etag(value, kind = :strong)
+      raise ArgumentError, ":strong or :weak expected" unless [:strong,:weak].include?(kind)
       value = '"%s"' % value
       value = 'W/' + value if kind == :weak
       response['ETag'] = value

test/helpers_test.rb

@@ -852,6 +852,16 @@ class HelpersTest < Test::Unit::TestCase
       get '/'
       assert_equal 'W/"FOO"', response['ETag']
     end
+
+    it 'raises an ArgumentError for an invalid strength' do
+      mock_app do
+        get '/' do
+          etag 'FOO', :w00t
+          "that's weak, dude."
+        end
+      end
+      assert_raise(ArgumentError) { get '/' }
+    end
   end
 
   describe 'back' do