Ruby on Rails

Hi everyone!

Im trying to install mechanizer from
http://github.com/tenderlove/mechanize.
I`ve clone the project into /tmp folder. When I do rake inside the
folder /tmp/mechanizer it gives me this error:

mac159180:mechanize renatosis$ rake
(in /private/tmp/mechanize)
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -w
-Ilib:bin:test:. -e 'require "rubygems"; require "test/unit"; require
"test/chain/test_argument_validator.rb"; require
"test/chain/test_auth_headers.rb"; require
"test/chain/test_custom_headers.rb"; require
"test/chain/test_header_resolver.rb"; require
"test/chain/test_parameter_resolver.rb"; require
"test/chain/test_request_resolver.rb"; require
"test/chain/test_response_reader.rb"; require
"test/test_authenticate.rb"; require "test/test_bad_links.rb"; require
"test/test_blank_form.rb"; require "test/test_checkboxes.rb"; require
"test/test_content_type.rb"; require "test/test_cookie_class.rb";
require "test/test_cookie_jar.rb"; require "test/test_cookies.rb";
require "test/test_encoded_links.rb"; require "test/test_errors.rb";
require "test/test_field_precedence.rb"; require
"test/test_follow_meta.rb"; require "test/test_form_action.rb"; require
"test/test_form_as_hash.rb"; require "test/test_form_button.rb"; require
"test/test_form_no_inputname.rb"; require "test/test_forms.rb"; require
"test/test_frames.rb"; require "test/test_get_headers.rb"; require
"test/test_gzipping.rb"; require "test/test_hash_api.rb"; require
"test/test_headers.rb"; require "test/test_history.rb"; require
"test/test_history_added.rb"; require "test/test_html_unscape_forms.rb";
require "test/test_if_modified_since.rb"; require "test/test_links.rb";
require "test/test_mech.rb"; require "test/test_mech_proxy.rb"; require
"test/test_mechanize_file.rb"; require "test/test_meta.rb"; require
"test/test_multi_select.rb"; require "test/test_no_attributes.rb";
require "test/test_option.rb"; require "test/test_page.rb"; require
"test/test_pluggable_parser.rb"; require "test/test_post_form.rb";
require "test/test_pretty_print.rb"; require "test/test_radiobutton.rb";
require "test/test_redirect_limit_reached.rb"; require
"test/test_redirect_verb_handling.rb"; require "test/test_referer.rb";
require "test/test_relative_links.rb"; require "test/test_request.rb";
require "test/test_response_code.rb"; require "test/test_save_file.rb";
require "test/test_scheme.rb"; require "test/test_select.rb"; require
"test/test_select_all.rb"; require "test/test_select_none.rb"; require
"test/test_select_noopts.rb"; require "test/test_set_fields.rb"; require
"test/test_ssl_server.rb"; require "test/test_subclass.rb"; require
"test/test_textarea.rb"; require "test/test_upload.rb"; require
"test/test_util.rb"; require "test/test_verbs.rb"' --
Loaded suite -e
Started
...............................................................E...........................................................................................................................................................................................................................................EEEE.EE...
Finished in 1.068686 seconds.

 1) Error:
test_post_multipart(FormsMechTest):
NoMethodError: undefined method `force_encoding' for
"Content-Disposition: form-data; name=\"first_name\"\r\n\r\n\r\n":String
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:387:in `submit'
   ./test/test_forms.rb:187:in `test_post_multipart'

 2) Error:
test_form_enctype(UploadMechTest):
NoMethodError: undefined method `force_encoding' for
"Content-Disposition: form-data; name=\"name\"\r\n\r\n\r\n":String
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:387:in `submit'
   ./test/test_upload.rb:29:in `test_form_enctype'

 3) Error:
test_form_io_obj(UploadMechTest):
NoMethodError: undefined method `force_encoding' for
"Content-Disposition: form-data; name=\"name\"\r\n\r\n\r\n":String
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:387:in `submit'
   ./test/test_upload.rb:83:in `test_form_io_obj'

 4) Error:
test_form_multipart(UploadMechTest):
NoMethodError: undefined method `force_encoding' for
"Content-Disposition: form-data; name=\"name\"\r\n\r\n\r\n":String
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:387:in `submit'
   ./test/test_upload.rb:52:in `test_form_multipart'

 5) Error:
test_form_read_file(UploadMechTest):
NoMethodError: undefined method `force_encoding' for
"Content-Disposition: form-data; name=\"name\"\r\n\r\n\r\n":String
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:387:in `submit'
   ./test/test_upload.rb:66:in `test_form_read_file'

 6) Error:
test_submit_no_file(UploadMechTest):
NoMethodError: undefined method `force_encoding' for
"Content-Disposition: form-data; name=\"name\"\r\n\r\nAaron\r\n":String
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:387:in `submit'
   ./test/test_upload.rb:96:in `test_submit_no_file'

 7) Error:
test_upload_with_post_param(UploadMechTest):
NoMethodError: undefined method `force_encoding' for
#<String:0x102401188>
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize/form.rb:229:in `collect'
   ./lib/mechanize/form.rb:229:in `request_data'
   ./lib/mechanize.rb:483:in `post_form'
   ./lib/mechanize.rb:374:in `post'
   ./test/test_upload.rb:10:in `test_upload_with_post_param'

309 tests, 1510 assertions, 0 failures, 7 errors
rake aborted!
Command failed with status (1):
[/System/Library/Frameworks/Ruby.framework/...]

(See full trace by running task with --trace)




Can you help me?
Thanks in advance.

Renato