sinatra_app.rb

require 'sinatra'

# Define a route
get "/foo" do
  "x"
end

# Try to redefine it
get "/foo" do
  "y"
end

def app
  Sinatra::Application
end

# Require rack/test to get a convenient way to 
# interact with the Sinatra routes
require "rack/test"
include Rack::Test::Methods

# Now make a GET request to /foo. Since routes
# are not overridden, this will print 'x', not 'y'
puts (get "/foo").body 

# We can inspect the set of routes that Sinatra has.
# The output is:
#[/.*[^\/]$/, /^\/__sinatra__\/([^\/?&#]+)\.png$/, /^\/foo$/, /^\/foo$/]
# As you can see, the last two routes have a duplicate pattern
puts app.routes["GET"].map {|route| route.first}.inspect

set :run, false