How to test File Downloads with Capybara

Rails
1

A colleague of mine struggled with finding a good answer, so this is worth sharing.

The situation was:

How to verify the content downloaded when clicking on a link contains something using Capybara. Manual testing involves the file open dialog.

Here’s what we learned:

  1. You have to use Selenium with Capbara. capybara-webkit did not work.
  2. This answer on Stack Overflow contained a working solution (amongst many others tried).
  3. This article from CollectiveIdea is helpful: TESTING FILE DOWNLOADS WITH CAPYBARA AND CHROMEDRIVER

Works on OSX. Firefox 34.0.5

Spec:

  describe 'Download CSV' do
    let( :submission_email ){ 'foo@example.com' }
    let( :email_csv ){ "id,email,created_at\n1,#{ submission_email }," }

    specify do
      visit '/emails'
      expect( page ).to have_content 'Email Submissions'

      click_on 'Download CSV'

      expect( DownloadHelpers::download_content ).to include email_csv
    end
  end

Spec helper:

require 'shared/download_helper'

Capybara.register_driver :selenium do |app|
  profile = Selenium::WebDriver::Firefox::Profile.new
  profile['browser.download.dir'] = DownloadHelpers::PATH.to_s
  profile['browser.download.folderList'] = 2

  # Suppress "open with" dialog
  profile['browser.helperApps.neverAsk.saveToDisk'] = 'text/csv'
  Capybara::Selenium::Driver.new(app, :browser => :firefox, :profile => profile)
end

config.before( :each ) do
    DownloadHelpers::clear_downloads
end

shared/download_helper.rb:

module DownloadHelpers
  TIMEOUT = 1
  PATH    = Rails.root.join("tmp/downloads")

  extend self

  def downloads
    Dir[PATH.join("*")]
  end

  def download
    downloads.first
  end

  def download_content
    wait_for_download
    File.read(download)
  end

  def wait_for_download
    Timeout.timeout(TIMEOUT) do
      sleep 0.1 until downloaded?
    end
  end

  def downloaded?
    !downloading? && downloads.any?
  end

  def downloading?
    downloads.grep(/\.part$/).any?
  end

  def clear_downloads
    FileUtils.rm_f(downloads)
  end
end