output.txt

{:x=>"", :y=>""}
{:x=>"100", :y=>"2279"}
{:x=>"200", :y=>"2379"}
{:x=>"300", :y=>"2479"}

test.rb

require "watir-webdriver"
require "selenium-webdriver"
include Watir
browser = Browser.new :chrome
driver = browser.driver

driver.navigate.to "http://javascript.ru/ui/draganddrop#demo"

p :x => browser.element(:id => "mouseX").value, 
  :y => browser.element(:id => "mouseY").value
  
driver.action.move_by(100,100).perform

p :x => browser.element(:id => "mouseX").value, 
  :y => browser.element(:id => "mouseY").value

driver.action.move_by(100,100).perform

p :x => browser.element(:id => "mouseX").value, 
  :y => browser.element(:id => "mouseY").value

driver.action.move_by(100,100).perform

p :x => browser.element(:id => "mouseX").value, 
  :y => browser.element(:id => "mouseY").value