我正在尝试用 poltergeist 替换 capybara-webkit 驱动程序，以满足我需要 javascript 的规范。虽然我遇到了这个奇怪的错误，但我找不到其他人有同样的问题。运行访问命令时出现以下错误：
Failure/Error: visit edit_path(:model_name => "field_test", :id => @record.id)
NoMethodError:
undefined method `parser' for Faye::WebSocket:Class
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/web_socket_server.rb:20:in `initialize'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/web_socket_server.rb:99:in `new'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/web_socket_server.rb:99:in `accept'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/web_socket_server.rb:143:in `send'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/server.rb:29:in `send'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/browser.rb:168:in `command'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/browser.rb:21:in `visit'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/poltergeist-1.0.2/lib/capybara/poltergeist/driver.rb:81:in `visit'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/capybara-1.1.4/lib/capybara/session.rb:157:in `visit'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/capybara-1.1.4/lib/capybara/dsl.rb:161:in `visit'
# ./spec/integration/config/edit/rails_admin_config_edit_spec.rb:698:in `block (3 levels) in <top (required)>'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example.rb:114:in `instance_eval'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example.rb:114:in `block in run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example.rb:254:in `with_around_each_hooks'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example.rb:111:in `run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:390:in `block in run_examples'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:386:in `map'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:386:in `run_examples'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:371:in `run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:372:in `block in run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:372:in `map'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/example_group.rb:372:in `run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/command_line.rb:28:in `block (2 levels) in run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/command_line.rb:28:in `map'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/command_line.rb:28:in `block in run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/reporter.rb:34:in `report'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/command_line.rb:25:in `run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/runner.rb:80:in `run'
# /Users/myusername/.rvm/gems/ruby-1.9.3-p392@rails3/gems/rspec-core-2.13.1/lib/rspec/core/runner.rb:17:in `block in autorun'