A snapshot of the tests we use internally at GitHub to help edit our blog posts before they go out to everybody. For more information, take a peek at http://zachholman.com/posts/how-github-writes-blog-posts

emoji_test.rb

require_relative "test_helper"

require "open-uri"
require "net/http"

class EmojiTest < Blog::Test
  def test_no_emoji
    posts.each do |post|
      content = File.read(post)
      refute_match /:[a-zA-Z0-9_]+:/, content,
        "You have emoji in your post, which we try to avoid"
    end
  end
end

images_test.rb

require_relative "test_helper"

require "open-uri"
require "net/http"

class ImagesTest < Blog::Test
  def setup
    @images = posts.map do |post|
      content = File.read(post)
      md      = Redcarpet::Markdown.new(Redcarpet::Render::HTML, autolink: true, tables: true)
      html    = md.render(content)
      doc     = Nokogiri::HTML(html)

      doc.css("img").map do |img|
        url      = img.attribute("src").value
        uri      = URI(url)
        response = Net::HTTP.get_response(uri)

        { :url => url, :response => response, :element => img }
      end
    end.flatten
  end

  def test_images_arent_too_big
    large_images = @images.select { |img| img[:response].body.size.to_i > 1_000_000 }

    error_message = large_images.map do |img|
      "  #{img[:response].body.size} bytes: #{img[:url]}"
    end.join("\n")

    assert large_images.empty?,
      "The following images are over a megabyte in size... consider shrinking them:\n\n#{error_message}"
  end

  def test_images_have_alt_tags
    @images.select do |img|
      alt = img[:element].attribute("alt").value
      no_alt_tags = (alt.strip == "" || (alt =~ /^screen shot /))

      refute no_alt_tags,
        "Images need an alt tag for accessibility. Your image should have a short, one or two word description of the image in the ![] parts of your post."
    end
  end

  def test_images_are_dotcom_hosted
    @images.select do |img|
      url = img[:url]

      assert_match /^https:\/\/cloud\.githubusercontent\.com/, url,
        "Images should be hosted on GitHub. Try dragging an image into an issue comment, uploading it, and using that URL."
    end
  end

  def test_image_proportions
    @images.select do |img|
      width, height = FastImage.size(img[:url])

      assert width >= 1354,
        "Screenshots should be retina-quality — meaning at least 1354 pixels across — so they look good on higher-resolution screens. If you're taking a shot of a small interface element, consider zooming the page with cmd+plus and taking a screenshot that way; the blog will scale it down for you."

      assert (width/height.to_f) > 1.2,
        "Screenshots should be roughly panoramic (more than a 1.2 width:height ratio). Try taking a wider, shorter screenshot so it reduces the amount of scoll necessary to view the content of the blog post."
    end
  end
end

test_helper.rb

require "fileutils"

require "rubygems"
require "bundler/setup"
require "minitest/autorun"
require "fastimage"
require "nokogiri"
require "redcarpet"

cat = <<-'cat'



                                                   .--.
                                                   `.  \
                                                     \  \
                                                      .  \
                                                      :   .
                                                      |    .
                                                      |    :
                                                      |    |
      ..._  ___                                       |    |
     `."".`''''""--..___                              |    |
     ,-\  \             ""-...__         _____________/    |
     / ` " '                    `""""""""                  .
     \                                                      L
     (>                                                      \
    /                                                         \
    \_    ___..---.                                            L
      `--'         '.                                           \
                     .                                           \_
                    _/`.                                           `.._
                 .'     -.                                             `.
                /     __.-Y     /''''''-...___,...--------.._            |
               /   _."    |    /                ' .      \   '---..._    |
              /   /      /    /                _,. '    ,/           |   |
              \_,'     _.'   /              /''     _,-'            _|   |
                      '     /               `-----''               /     |
                      `...-'                                       !_____)


cat

puts cat
puts "
  Hello you lovely GitHub blog author person human!
  This is test output from your blog post you just wrote. Unlike most tests in
  life (and code!), it's *totally cool* to fail these tests. They're just here
  to catch anything you might have missed while writing your draft.
  Consider them suggestions rather than things you *need* to do before
  publishing your post.
  Happy shipping!
"

module Blog
  class Test < MiniTest::Test
    # All the posts we're interested in checking. This means we're looking at
    # files that have changed on this particular branch we're on.
    #
    # Returns an Array of String filenames.
    def posts
      diffable_files = `git diff --name-only --diff-filter=ACMRTUXB origin/master... | grep .md`.split("\n")

      posts = diffable_files.select do |filename|
        File.ctime(filename) > Time.new(2014,9,3)
      end

      posts
    end
  end
end

today_test.rb

require_relative "test_helper"

class TodayTest < Blog::Test
  def test_doesnt_start_with_today
    posts.each do |post|
      content = File.read(post)

      body_text = content.split("\n").delete_if do |line|
        line[0] == "#" || line.strip == ""
      end

      refute body_text.first =~ /Today/, "Posts usually shouldn't start with \"Today\""
    end
  end
end

@hobarrera I'm pretty sure they use Jekyll which allows writing of posts in markdown and is written in Ruby, which would make adding tests quite easy if you setup your own.