swap a port number when a cucumber scenario is tagged with varnish

gistfile1.rb

# Cucumber has a nice feature where it can wrap code _around_ a 
# scenario. In my case I have a Varnish cache running on port 6081
# and an plain apache on port 80 and various tests that rely
# on both services. So this way I can temporarily monkey patch the
# Capybara host if I tag any feature with '@varnish' and have the
# http traffic hit the cache.

Around('@varnish') do |scenario, block|
    default_host = Capybara.default_host 
    Capybara.default_host = Capybara.default_host.gsub(/(:\d+)$/, ':6081')
    block.call # run the scenario
    Capybara.default_host = default_host # put it back
end