gistfile1.rb

require 'mechanize'

[['username1', 'password1'], ['username2', 'password2']].each do |user|
  mech = Mechanize.new
  mech.verify_mode = 0
  page = mech.get 'http:// ... /oauth'
  form = page.form
  form.field_with(:name => /mail/i).value = user[0]
  form.field_with(:name => /pass/i).value = user[1]
  result = form.submit.link_with(:text=> /continue/).click
  result.body =~ /logout/
end