check.rb

s.fill_in :guess_3, with: 6857
s.fill_in :captcha, with: 71355
s.click_button 'Check'

s.save_screenshot 'check.png'

Gemfile

source 'https://rubygems.org'

gem 'capybara-webkit'

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    capybara (2.4.4)
      mime-types (>= 1.16)
      nokogiri (>= 1.3.3)
      rack (>= 1.0.0)
      rack-test (>= 0.5.4)
      xpath (~> 2.0)
    capybara-webkit (1.3.1)
      capybara (>= 2.0.2, < 2.5.0)
      json
    json (1.8.1)
    mime-types (2.4.3)
    mini_portile (0.6.1)
    nokogiri (1.6.5)
      mini_portile (~> 0.6.0)
    rack (1.5.2)
    rack-test (0.6.2)
      rack (>= 1.0)
    xpath (2.0.0)
      nokogiri (~> 1.3)

PLATFORMS
  ruby

DEPENDENCIES
  capybara-webkit

node.rb

rows.first.class
#=> Capybara::Node::Element

[28] pry(main)> ls rows.first
Capybara::Node::Finders#methods: all  field_labeled  find  find_button  find_by_id  find_field  find_link  first
Capybara::Node::Actions#methods:
  attach_file  check  choose  click_button  click_link  click_link_or_button  click_on  fill_in  select  uncheck  unselect
Capybara::Node::Matchers#methods:
  ==                  has_button?         has_link?              has_no_field?     has_no_text?             has_table?
  assert_no_selector  has_checked_field?  has_no_button?         has_no_link?      has_no_unchecked_field?  has_text?
  assert_no_text      has_content?        has_no_checked_field?  has_no_select?    has_no_xpath?            has_unchecked_field?
  assert_selector     has_css?            has_no_content?        has_no_selector?  has_select?              has_xpath?
  assert_text         has_field?          has_no_css?            has_no_table?     has_selector?            refute_selector
Capybara::Node::Base#methods: base  find_css  find_xpath  parent  session  synchronize
Capybara::Node::Element#methods:
  []             checked?  disabled?     drag_to  inspect  path    right_click    selected?  tag_name  trigger          value
  allow_reload!  click     double_click  hover    native   reload  select_option  set        text      unselect_option  visible?

prob.rb

s.find('.problem_content').text
=> "The prime factors of 13195 are 5, 7, 13 and 29. What is the largest prime factor of the number 600851475143 ?"

sample.rb

within("#login-form") do
  fill_in 'email',    with: 'user@example.com'
  fill_in 'password', with: 'password'
end
click_button 'ログイン'

screenshot.rb

s.save_screenshot 'signin.png'

signin.rb

require 'bundler/setup'
Bundler.require

Capybara.javascript_driver = :webkit
s = Capybara::Session.new(:webkit)

s.visit 'https://projecteuler.net/about'
s.click_link 'Sign In'

solve.rb

require 'prime'

13195.prime_division
# => [[5, 1], [7, 1], [13, 1], [29, 1]]

600851475143.prime_division
# => [[71, 1], [839, 1], [1471, 1], [6857, 1]]
600851475143.prime_division.map{|pair| pair.first }.max
# => 6857

submit.rb

s.fill_in :username, with: 'yourusername'
s.fill_in :password, with: 'yourpassword'
s.click_button 'Sign In'

table.rb

class Problem < Struct.new(:id, :title, :solved)
  def url
    'https://projecteuler.net/problem=' + id.to_s
  end
end

rows = s.all('#problems_table > tbody > tr').drop(1) # dropでヘッダー行を取り除く

# テーブルの情報を元に各行からProblemインスタンスを生成
problems = rows.map do |row|
  cells = row.all('td')
  Problem.new(*[cells[0].text.to_i, cells[1].text, cells[3].text.length > 0])
end

problems.take(4)
# => [#<struct Problem id=1, title="Multiples of 3 and 5",       solved=true>,
#     #<struct Problem id=2, title="Even Fibonacci numbers",     solved=true>,
#     #<struct Problem id=3, title="Largest prime factor",       solved=false>,
#     #<struct Problem id=4, title="Largest palindrome product", solved=false>]

# まだ解いてない問題をひとつ選び、問題ページを開く
problem = problems.select{|p| !p.solved }.first

s.visit problem.url