capybara-webkitにはデバッグモードが存在する。

spec/spec_helper.rb

Capybara.javascript_driver = :webkit_debug

すごく遅いexampleを実行
bundle exec spring rspec spec/features/top_page_spec.rb

Finished "EnableLogging" with response "Success()"
Wrote response true ""
Received "Visit"
Started "Visit"
Load started
"Visit" started page load
Started request to "http://127.0.0.1:62146/"
Finished "Visit" with response "Success()"
Started request to "http://127.0.0.1:62146/assets/application.css"
Started request to "http://127.0.0.1:62146/assets/application.js"
Received 200 from "http://127.0.0.1:62146/"
Received 200 from "http://127.0.0.1:62146/assets/application.css"
Received 200 from "http://127.0.0.1:62146/assets/application.js"
Started request to "http://www.google-analytics.com/analytics.js"
Started request to "http://127.0.0.1:62146/assets/common/logo.png"
Received 200 from "http://127.0.0.1:62146/assets/common/logo.png"
※ ここで動かなくなる

google analyticsがブロックしてました