slow_requests_for_debugging.rb

# This is a debugging tool for flaky ruby/rack (rails) browser tests not properly
# waiting for potentially slow server responses (eg. with Capybara). Its a Rack
# middleware that adds a delay to every response, thus making the problem
# evident.
#
# In Rails, add the following to the end of your Application class definition in
# `config/application.rb`, AND REMOVE AFTER DEBUGGING!!!
#
#     # TODO: REMOVE!!
#     require("slow_requests_for_debugging")
#     config.middleware.use SlowRequestsForDebugging
#
class SlowRequestsForDebugging
  DELAY_SECS = 5

  def initialize(app)
    @app = app
  end

  def call(env)
    @request = Rack::Request.new(env)
    puts "Holding for #{DELAY_SECS} seconds the response to #{@request.url}"
    sleep(DELAY_SECS)
    puts "Response hold released for " + @request.url
    @app.call(env)
  end
end

Other reasons for flaky tests:

• Outstanding requests leaking to next test: Close the browser session on test teardown.
• Overlapping DOM elements blocking interaction: Check browser screenshots on failing tests.