ActiveAdmin and Markdown on your 15 minute blog - Part 4

Leonard Garvey
May 27, 2013

Adding ActiveAdmin and Markdown support to Rails

Welcome back to reInteractive’s Ruby on Rails 15 minute blog tutorial series. If you haven’t started following through the series and you’re new to Rails then you might want to start with the first post. Today we’ll be following directly on from [Part 3] ( If you feel confident with Rails but want to learn more about ActiveAdmin and/or Markdown you can find some instructions on getting the code set up properly below.

Installing an Administration System

One of the big problems with our blog is that we’re using HTTP Basic Authentication to prevent anyone from creating and editing blog posts and that the links to perform these actions are right there in the blog. Instead we’d prefer to have an admin panel where we could manage our blog posts. We could build one from scratch but there’s a fantastic gem called ActiveAdmin which we can use to easily give us what we want.

Application Setup

You’ll need to have been following our InstallFest blog posts starting with and have completed If you’ve done this but want to start with some fresh code, you can by copying the tag that’s available in the public git repository. which you can download to your computer here.

Download the zip file, unpack it to a folder on your computer and commit it to git using the following prompt commands:

sh bundle install rake db:create db:setup git add . git commit -m "Restarting the 15 minute blog"

You’ll need to refer to this post if you want to get it setup on Heroku.

Lets dive into installing ActiveAdmin.

Installing ActiveAdmin

Open your Gemfile and add the following to the bottom of the file:

ruby gem 'activeadmin' gem "meta_search", '>= 1.1.0.pre'

Then in your terminal run bundle install to install ActiveAdmin. Once bundle has finished you need to run:

sh rails generate active_admin:install rake db:migrate

Finally restart your rails server by changing to the terminal with it running, stopping it with Ctrl-c and then restarting it with rails s. Now you can open your browser to http://localhost:3000/admin and log into your new admin interface using the default credentials: and password.

Implement a failing test

We’re about to start implementing some functionality which means we should first write a test. This test will fail until we finish our implementation. Because this feature is primarily aimed at the user interface of our application we’ll be editing and adding additional feature specs.

Open spec/features/managing_posts_spec.rb and change the contents of this file to match:

ruby require 'spec_helper' feature 'Managing blog posts' do scenario 'Guests cannot create posts' do visit root_path expect(page).to_not have_link 'New Post' end context 'as an admin user' do background do email = '' password = 'password' @admin = AdminUser.create(:email => email, :password => password) log_in_admin_user end def log_in_admin_user(email = '', password = 'password') reset_session! visit admin_root_path fill_in 'Email', :with => email fill_in 'Password', :with => password click_button 'Login' end scenario 'Posting a new blog' do click_link 'Posts' click_link 'New Post' fill_in 'post_title', :with => 'New Blog Post' fill_in 'post_body', :with => 'This post was made from the Admin Interface' click_button 'Create Post' expect(page).to have_content 'This post was made from the Admin Interface' end context 'with an existing blog post' do background do @post = Post.create(:title => 'Awesome Blog Post', :body => 'Lorem ipsum dolor sit amet') end scenario 'Editing an existing blog' do visit admin_post_path(@post) click_link 'Edit' fill_in 'Title', :with => 'Not really Awesome Blog Post' click_button 'Update Post' expect(page).to have_content 'Not really Awesome Blog Post' end end end end

Saving and then running this spec with rspec spec/features/managing_posts_spec.rb --order default should result in several errors. We should go through these errors quickly so we can see what we’re testing so that the solution is more understandable. Note that we’re running our spec here in the order as written and not in a random order which is the default. This is so that your output will be as close as possible to the below:

sh Failures: 1) Managing blog posts Guests cannot create posts Failure/Error: expect(page).to_not have_link 'New Post' Capybara::ExpectationNotMet: expected not to find link "New Post", found 1 match: "New Post" # ./spec/features/managing_posts_spec.rb:6:in `block (2 levels) in <top (required)>'

If you look at the first scenario in the test what we’re checking is that a guest cannot create a post. Specifically we want to ensure that there isn’t a link called “New Post” on the post index page. Currently this link exists so we experience our first test failure.

sh 2) Managing blog posts as an admin user Posting a new blog Failure/Error: click_link 'Posts' Capybara::ElementNotFound: Unable to find link "Posts" # ./spec/features/managing_posts_spec.rb:27:in `block (3 levels) in <top (required)>'

As an admin user we’d expect to be able to log into the admin panel, click a ‘Posts’ link and then create a post. At the moment we don’t have that ‘Posts’ link so this scenario fails too.

sh 3) Managing blog posts as an admin user with an existing blog post Editing an existing blog Failure/Error: visit admin_post_path(@post) NoMethodError: undefined method `admin_post_path' for #<RSpec::Core::ExampleGroup::Nested_1::Nested_1::Nested_1:0x007fea116d89b0> # ./spec/features/managing_posts_spec.rb:43:in `block (4 levels) in <top (required)>' Finished in 0.24472 seconds 3 examples, 3 failures

Finally this scenario fails because we haven’t created the posts section of our admin panel yet. Let’s do that now. Run: rails generate active_admin:resource Post. You could open up the browser and manually check that this did what you want, instead you can just re-run the spec (rspec spec/features/managing_posts_spec.rb --order default). This time we receive only 1 error:

sh Failures: 1) Managing blog posts Guests cannot create posts Failure/Error: expect(page).to_not have_link 'New Post' Capybara::ExpectationNotMet: expected not to find link "New Post", found 1 match: "New Post" # ./spec/features/managing_posts_spec.rb:6:in `block (2 levels) in <top (required)>' Finished in 0.66099 seconds 3 examples, 1 failure

We can fix this scenario by opening: app/views/posts/index.html.erb and deleting:

erb <%= link_to 'New Post', new_post_path %>

Save that and rerun our spec which should pass or “go green”. Some of you might already be protesting that we still have the backend code for adding a post and all we’ve done is remove the link in the HTML and you’re completely correctly. We need to remove code from our controller and configure our routes so that there is absolutely no way to create or edit a post except in the admin panel.

Open: app/controllers/posts_controller.rb and delete all the methods except for index and show! You can also delete the authenticate method and the before_filter line. Your PostsController should look like the following when you’ve finished:

ruby class PostsController < ApplicationController # GET /posts # GET /posts.json # GET /posts.atom def index @posts = Post.all respond_to do |format| format.html # index.html.erb format.json { render json: @posts } format.atom end end # GET /posts/1 # GET /posts/1.json def show @post = Post.find(params[:id]) respond_to do |format| format.html # show.html.erb format.json { render json: @post } end end end

Save those changes. Since we’ve made a large change to one of our main controllers now would be a good time to run our entire test suite. You’ll actually see that everything passes but there’s a curious new spec that we didn’t create. This was created automatically for you when you installed ActiveAdmin. Since there’s no functionality in there that we wrote we’re going to simply delete the spec. On OSX or Linux run rm spec/models/admin_user_spec.rb and on windows run del spec\models\admin_user_spec.rb.

Cleaning up and Committing

We’re at a good spot! We’ve created an admin panel and wrote a test before even started implementing it. Thanks to the power of ActiveAdmin we were able to implement it extremely quickly, don’t be misled into thinking that all Rails apps are this simple though. In any case we should run all our tests to ensure that everything is working, then commit our code.

Run: rspec

Ensure everything passes then run:

sh git add . git commit -m "added ActiveAdmin and a Posting admin interface"

Adding Markdown formatting support to posts

One feature we’d love to have on our blog is the ability to author our blog posts using Github-style Markdown. Luckily doing this in Ruby is really easy and integrating it in Rails should only take a few lines of code. We’ll be using the excellent redcarpet markdown engine, and the rouge code highlightning utility.

Note to people who are following along and can’t compile gems with native extensions. You can skip following section and use the pure Ruby Maruku gem for markdown support instead. You can head to: to find a guide on how to do this next section using the Maruku gem instead.

Let’s get started by writing a failing test for our markdown service first.

Writing a failing MarkdownService spec

We’re going to be creating a class for our Rails application that takes markdown formatted text and returns HTML. There is some disagreement in the Rails community as to where custom code should be placed. Some people prefer to use the lib folder, but I prefer to put application code in app/<directory>. In this case we’ll be creating a service so we’ll first be making two folders: app/services and spec/services. Also create a file spec/services/markdown_service_spec.rb. This test will look like:

ruby require 'spec_helper' describe MarkdownService do it { should be_a MarkdownService } end

This is the most basic spec that simply states that there should be a class called MarkdownService. Run this spec with rspec spec/services you’ll receive an error:

sh spec/services/markdown_service_spec.rb:3:in `<top (required)>': uninitialized constant MarkdownService (NameError)

This simply tells us that we haven’t created the class yet. Create a file app/services/markdown_service.rb with the contents:

ruby class MarkdownService end

And rerun our spec with rspec spec/services. This time the spec will pass. Obviously this class doesn’t do anything yet so we’ll need to write another test. Open spec/services/markdown_service_spec.rb and we’ll write the test for a render method.

If you have decided to use the pure-ruby Maruku gem for Markdown then The contents of this spec file will look like:

ruby require 'spec_helper' describe MarkdownService do it { should be_a MarkdownService } describe '#render' do let(:content) { "anything" } # we don't care what content gets rendered # the markdown engine is just a test double we can monitor in our test let(:markdown_engine) { double('Markdown') } before do # Stub out the redcarpet markdown engine # In our test we can assume it works properly # since it's a well tested library. Redcarpet::Markdown.stub(:new) { markdown_engine } end it 'should delegate to the markdown engine' do # Set up the expectation of what our code should accomplish markdown_engine.should_receive(:render).with(content) end end end

This is a pretty big jump. But effectively this test is saying that the markdown_engine will receive the render command with the content argument. Then we call MarkdownService#render. There’s definitely some advanced Ruby magic going on here and it’s totally fine if for the moment you don’t understand it fully. Also don’t expect to be able to always TDD new code. Often you need to prototype the implementation before you write the test. Save the spec file and run your spec again. This time you’ll receive another failure so it’s time to open the class we’re testing again (app/services/markdown_service.rb) and update the contents to: ruby require 'rouge/plugins/redcarpet' class MarkdownService class HTMLWithRouge < Redcarpet::Render::HTML include Rouge::Plugins::Redcarpet # yep, that's it. end def initialize @markdown =, :fenced_code_blocks => true) end def render(text) @markdown.render(text) end end

Re-running our spec everything should now pass.

As a user I want to write Posts in Markdown

We’ve implemented a utility class for converting a markdown string into HTML, but we still need to properly integrate that into our Rails application. We should write a feature spec to make sure that this feature works properly. Create a file: spec/features/writing_posts_spec.rb with the following content.

ruby require 'spec_helper' feature 'Writing blog posts' do background do email = '' password = 'password' @admin = AdminUser.create(:email => email, :password => password) log_in_admin_user end def log_in_admin_user(email = '', password = 'password') reset_session! visit admin_root_path fill_in 'Email', :with => email fill_in 'Password', :with => password click_button 'Login' end scenario 'Writing a blog post in markdown' do click_link 'Posts' click_link 'New Post' fill_in 'post_title', :with => 'New Blog Post' fill_in 'post_body', :with => "[ link](" click_button 'Create Post' visit post_path(Post.last) page.should have_link ' link' end end

What we’re automating here is logging into the Admin panel, creating a post with a markdown link, navigating to the post we’ve just created and then checking that the post is rendered correctly in HTML. When we run this new spec (using rspec spec/features/writing_posts_spec.rb) we are told:

sh expected to find link " link" but there were no matches

The problem is that right now our blog application just spits out the text roughly as entered into the database. The quickest way of doing this is to give our model the ability to convert it’s contents to HTML. Let’s write a test for that.

Open: spec/models/post_spec.rb and update it to read:

ruby require 'spec_helper' describe Post do describe 'validations' do subject(:post) { } # sets the subject of this describe block before { post.valid? } # runs a precondition for the test/s [:title, :body].each do |attribute| it "should validate presence of #{attribute}" do expect(post).to have_at_least(1).error_on(attribute) expect(post.errors.messages[attribute]).to include "can't be blank" end end end describe '#content' do # Create a double of the MarkdownService let(:markdown_service) { double('MarkdownService') } before do # We don't want to use the actual MarkdownService # since it's tested elsewhere! MarkdownService.stub(:new) { markdown_service } end it 'should convert its body to markdown' do markdown_service.should_receive(:render).with('post body') => 'post body').content end end end

What we’ve done here is added a test for a content method which will convert the body of the Post object into HTML using the MarkdownService we wrote earlier. Since we’ve already tested the MarkdownService we’ll stub it out just like we stubbed out the markdown engine itself in our MarkdownService test.

Run that spec (using rspec spec/models/post_spec.rb) and notice that it’s failing. We still need to provide the implementation to make this test pass. Open: app/models/post.rb and provide the implementation for the render method:

ruby class Post < ActiveRecord::Base attr_accessible :body, :title has_many :comments validates_presence_of :body, :title def content end end

Save this and re-run our post model spec and observe that everything now passes!

At this stage if we run all our specs (simply type rspec) we’ll see we still only have 1 failure. There’s only 1 line of code needed to make this feature spec pass so lets open: app/views/posts/_post.html.erb and update it to use the Post#content method we wrote earlier.


<%= link_to_unless_current post.title, post %>

<%= post.content.html_safe %> ```

One thing to note is that since we want to render the HTML generated by our markdown engine as HTML and not have it be automatically escapped by the Rails view we need to convert it to a SafeBuffer using the html_safe method call.

Save that and rerun all our specs again (using rspec). Success! All our specs pass and we’ve implemented that entire feature without even opening the browser once. Implementing a feature in this way feels very liberating and can be very fast. It means that as a developer you can focus on the implementation and leave the front-end UI code for later (or for a specialist).

Installing a stylesheet for code highlighting

Note: if you used Maruku instead of Redcarpet you can skip this section. One great thing about the Redcarpet/Rouge combo is that it fully supports Github style markdown including code blocks. We just need to install a stylesheet which will support it.

Download: into vendor/assets/stylesheets and then open app/assets/stylesheets/foundation_and_overrides.scss and put the following line at the bottom:

ruby @import 'github';

This informs the Rails asset pipeline that you’d like to include the code stylesheet you just downloaded into your application.

Cleaning up

Commit all those changes with:

sh git add . git commit -m "Added markdown support for blog posts"

This might be a good time to push to Heroku too. Do that by typing

sh git push heroku master

Next Steps

Up next we’ll add features to your blog and learn more about Rails migrations. Click here to check it out and continue your Rails adventure.

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