I run my tests in parallel by opening more than one command window and
specifying a different port.
webdriver:
driver = Selenium::WebDriver.for(:remote, :url => "http://
127.0.0.1:4444/wd/hub", :desired_capabilities => :chrome)
port 4444 is default but you can specify by using -port switch
i.e. start selenium server specifying the port
java -jar selenium-server-standalone-2.8.0.jar -port 3030
driver = Selenium::WebDriver.for(:remote, :url => "http://
127.0.0.1:3030/wd/hub", :desired_capabilities => :chrome)
This may or may not solve the cookie problem but it will definitely
run in parallel.