The Watir-WebDriver-Performance gem aims to provide a set of navigation timing metrics for Watir-WebDriver actions using a W3C page performance standard. This is a perfect solution to capture response time metrics, and it’s very straightforward to do but currently only works in Chrome and IE9l, so there’s no Firefox support.

require 'watir-webdriver'
require 'watir-webdriver-performance'

b = Watir::Browser.new :chrome

10.times do
  b.goto 'http://watir.com'
  load_secs = b.performance.summary[:response_time]/1000 
  puts "Load Time: #{load_secs} seconds."
end  

This produces something like:

Load Time: 3.701 seconds.
Load Time: 0.694 seconds.
Load Time: 1.874 seconds.
Load Time: 1.721 seconds.
Load Time: 2.096 seconds.
Load Time: 0.823 seconds.
Load Time: 2.362 seconds.
Load Time: 1.008 seconds.
Load Time: 1.761 seconds.
Load Time: 2.066 seconds.

List of available metric groupings

• :summary
• :navigation
• :memory
• :timing