def test_uniqueness_of_screen_name_and_email
  user_repeat = User.new(:screen_name => @valid_user.screen_name,
                         :email => @valid_user.email,
                         :password => @valid_user.password)
  assert !user_repeat.valid?
  assert_equal "jest ju zajty.", user_repeat.errors.on(:screen_name)
  assert_equal "jest ju zajty.", user_repeat.errors.on(:email)
end

