I’ve gotten a lot of mileage out of RSpec plus Capybara for integration testing my Ruby apps lately.

obligatory Capybara pic

Executing JavaScript with Capybara used to be a pain, but I recently switched from capybara-webkit to Poltergeist as my JS test driver.

Poltergeist uses PhantomJS, which in my experience is faster than capybara-webkit and easier to install.1

Sadly, Sam Raimi will be subjecting Poltergeist to the ole' Hollywood remake

Poltergeist supports the required Capybara driver API as well as a few additional features such as taking screenshots.

I wrote a little helper method around taking screenshots, which:

  1. generates a name for the output file (because I usually don’t care)
  2. puts the file in the trash for me (or in /tmp if there is no trash)
  3. renders the entire page (overridable when I just want the viewport)
  4. opens it in Preview (or whatever the default app for .png is)

Not ground breaking, but pretty cool in practice. I call it snap!.2 Here’s the method:

def snap!(options={})
  path = options.fetch :path, "~/.Trash"
  file = options.fetch :file, "#{Time.now.to_i}.png"
  full = options.fetch :full, true

  path = File.expand_path path
  path = "/tmp" if !File.exists?(path)

  uri = File.join path, file

  page.driver.render uri, full: full
  system "open #{uri}"

Drop it anywhere that RSpec will load it3 and use it in your integration tests when your JavaScript is misbehaving:

feature "search autocomplete" do
  scenario "from the homepage", js: true do
    visit "/"
    fill_in "search", with: "Jero"
    expect(page).to have_content "Jerod Santo"

In this example, you could visually inspect whether the autocomplete is just not showing up at all or if it is showing up and just has the wrong content in it.

A fringe benefit of using the snap! method is that it calls page.driver.render, which will raise an error when the active driver doesn’t have the method.

Capybara’s default driver, RackTest, doesn’t have it so you’ll know right away if your test is just failing because you forgot the js: true flag in the enclosing block.

That one has bit me more than once!

  1. PhantomJS bundles Qt so you don’t have to install it yourself

  2. I’m using the ! bang suffix for no other reason then it makes the method more fun to call

  3. when using rspec-rails you can just drop it in spec/support