Thursday, April 7, 2011

Object oriented acceptance testing

In my last blog post I highlighted the two problems that I have with Cucumber for acceptance testing:

  1. It's difficult to get the customer to write/read Cucumber scenarios
  2. Cucumber scenarios most of the time are procedural programming.

The story

Being aware of the problems mentioned above I started experimenting with my side project to find a better way. I prefer trying out new ways on my side project instead of on the client work. The project is a social network app for board game geeks. As with every social app the interaction between users is quite high. People can vote for good games, comment on other people votes, write game reviews etc. I started writing tests in the following format:

user =
user.visit_main_page "Login"
user.fills_in :login, :with ="andrzej"

As you see it's a fairly normal Ruby code with API similar to what Capybara/Webrat offers out of the box. In fact, I use Steak with Capybara.

Ruby code

When you compare it to the Cucumber style, the main difference is that it's Ruby code. If it's so hard to convince the customers to write scenarios then I see no point in inventing and using a new language. We all love Ruby.


If it's mostly programmers who read the scenarios, then Ruby is the best choice. It's programmer-friendly and I think many programmers would parse the Ruby code above more easily than the Cucumber way:
Given a new user
When he visits the main page
And he follows "Login"
And he fills in "Login" with "Andrzej"

User object

In most apps the concept of User is very important. Why not making it an object? It simplifies a lot and you can hide some implementation details in the (Test)User class. You can create methods and reuse the implementation in an easier (IMO) way than reusing step definitions in Cucumber.

Everything is an object

In fact when you start working this way, you quickly realize that there are more objects appearing in your test world. You will probably have a Website object which can keep some implementation details, like the path to admin panel or methods responsible for setting up the application state.

You can also have objects encapsulating certain pages, if it's useful, or objects for some of your website widgets - sidebar, search_box etc.

Object oriented programming

As you see it's all about the good old OOP that we use in our production code. This solves my problem with Cucumber being too procedural. I can write code like:
user.should_see("Popular games", :inside => sidebar)
Whatever OOP style you like, you can use in your tests. Sounds good to have all pages being subclasses of Page? Write it so.

Human readable

I complain about the fact that it's hard to get customers read/write the scenarios. Cucumber is human readable, no doubts about it. However, if you look at the OOP code - is it not human readable? It takes discipline to have all your methods well named, but it's so worth it. 

I claim that this kind of code is still readable to our non-programmers stakeholders.


If you agree that it's readable, then you can actually think of your scenarios as the documentation. Nothing different here, as compared to Cucumber. If you organize your test objects nicely then you not only have a scenario view but also you can see what are the widgets responsible for or what is possible for the Guest user and what is possible for the logged-in User.


I found it hard to implement interaction between users in a Cucumber style of testing. I mean things like this:
andrzej = TestUser("andrzej", "password")
john = TestUser("john", "password")
andrzej.writes_a_review("Agricola", "content")
john.should_see "content"
john.comments("nice review!")
andrzej.should_receive_email("nice review!",  "john")

I think it's readable and if you hide the details in methods then the scenario reads very well. You can easily introduce new users into the interaction.


Personas is a concept in which you find the different types of users who interact with your app. You can give them names, describe what they do, what matters to them etc. This concept can help you think about new features in terms of which persona would use the feature in what way.

In your scenarios you can then use the persona to highlight which aspect of the feature you test. If you worry about security of the new feature then have a user in mind who can hack into your website and write scenarios to ensure it's not possible.
little_bobby_tables.fills_in :login, :with => "Robert'); DROP TABLE Users;--")


When I started with this kind of acceptance testing I didn't think it was so useful at first. When I showed it to my colleagues they quickly started using it as well. Special thanks to Paweł Pacana, who used it in our Ruby User Group website and published it to Github. Since then we started using this approach in our client projects and it works really well. I think it brings back the joy of writing acceptance tests.

I call this approach "object oriented acceptance testing" but my friends started calling it "common.rb" as the main test file that I used. Here is an excerpt from the first version of my common.rb file:
class TestUser
  attr_accessor :steak
  attr_accessor :email
  attr_accessor :password
  attr_accessor :login

  def initialize(steak)
    @steak = steak
    yield if block_given?

  def click(*args);     steak.click_link_or_button(*args) end
  def choose(*args);    steak.choose(*args) end
  def select(*args);*args) end
  def fill_in(*args);   steak.fill_in(*args) end
  def visit(path);      steak.visit(path) end
  def attach_file(*args);      steak.attach_file(*args) end
  def should_see(text); == true end
  def should_not_see(text); end
  def should_receive_email(text) 
    steak.find_email(@email, :with_text => text).should_not == nil
If you want to see more, look here:

All of the scenarios are kept in spec/acceptance, so look around how it works.

Not a gem, an approach

I was asked to release it as a gem. After some thinking I decided not to do that, as this would make it limiting. I prefer to think about it as an approach, not a specific technology. It all comes down to: Use object in your acceptance tests

The technology I choose is Capybara + Steak. Steak is a very simple DSL around RSpec. Since I started Capybara already provided a replacement for Steak, so it's no longer needed.

This approach is not web specific. In fact, we have a project which consists of a server written in Ruby with EventMachine which has no views but just exposes an API. We write test scenarios using objects that simulate clients connecting to the API. It works very well with typical acceptance tests but also with load testing.


As you see the approach is not revolutionary and I know that I'm not the first developer who uses it. There are not so many articles about it and I hope it can become more popular. Obviously, it doesn't solve all of the problems that exist in acceptance testing.

We still need to think how to make acceptance tests run quickly or solve the problem of preparing the application state for testing. I think we can do better than using Factories or Fixtures in acceptance tests and I have some ideas for simplifying it. I will present how it works in my next blog posts. Stay tuned. Thanks for reading.

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Seban said...

I've never used acceptance tests in real project- I don't need to I prefer good old-school unit testing. But your way is nice for me. I think it is better for programmer. Waiting to hear more about yours ideas about acceptance testing.
BTW. I like board games! ;)

Andrzej Krzywda said...



I would not be able to work without acceptance tests. Unit tests are important but there is lots of problems that can appear at the integration level.

Feel free to register at :)

Jo Liss said...

I like your TestUser class -- I think it's a great way to do Cucumber step definitions in actual Ruby code.

One thing though, perhaps it's better to not have should_ methods, but rather plain predicates. So instead of user.should_see('foo'), I'd suggest doing user.should see('foo'), where TestUser#sees? is a predicate method.

Andrzej Krzywda said...


Yes, I also prefer to have the steps calls in Ruby.

You're right, having it as #see would be the RSpec-way. Thanks. I'm still not sure if going with the Steak/Rspec combination is the best way. Next project I'm starting with Capybara + minitest and see if it's easier without RSpec magic.