Introducing Spectie, a behavior-driven-development library for RSpec 12

Posted by ryan Mon, 02 Nov 2009 03:34:00 GMT

I'm a firm believer in the importance of top-down and behavior-driven development. I often start writing an integration test as the first step to implementing a story. When I started doing Rails development, the expressiveness of Ruby encouraged me to start building a DSL to easily express the way I most-often wrote integration tests. In the pre-RSpec days, this was just a subclass of ActionController::IntegrationTest that encapsulated the session management code to simplify authoring tests from the perspective of a single user. As the behavior-driven development idea started taking hold, I adapted the DSL to more-closely match those concepts, and finally integrated it with RSpec. The result of this effort was Spectie (rhymes with necktie).

The primary goal of Spectie is to provide a simple, straight-forward way for developers to write BDD-style integration tests for their projects in a way that is most natural to them, using existing practices and idioms of the Ruby language.

Here is a simple example of the Spectie syntax in a Rails integration test:

Feature "Compelling Feature" do
  Scenario "As a user, I would like to use a compelling feature" do
    Given :i_have_an_account, :email => "ryan@kinderman.net"
    And   :i_have_logged_in

    When  :i_access_a_compelling_feature

    Then  :i_am_presented_with_stunning_results
  end

  def i_have_an_account(options)
    @user = create_user(options[:email])
  end

  def i_have_logged_in
    log_in_as @user
  end

  def i_access_a_compelling_feature
    get compelling_feature_path
    response.should be_success
  end 

  def i_am_presented_with_stunning_results
    response.should have_text("Simply stunning!")
  end
end

Install

Spectie is available on GitHub, Gemcutter, and RubyForge. The following should get it installed quickly for most people:

% sudo gem install spectie

For more information on using Spectie, visit http://github.com/ryankinderman/spectie.

Why not Cucumber or Coulda?

At the time that this is being written, Cucumber is the new hotness in BDD integration testing. My reasons for sticking with Spectie instead of switching to Cucumber like the rest of the world are as follows:

  • Using regular expressions in place of normal Ruby method names seems like a potential maintenance nightmare, above and beyond the usual potential.
  • The layer of indirection that is created in order to write tests in plain text doesn't seem worth the cost of maintenance in most cases.
  • Separating a feature from its "step definitions" seems mostly unnecessary. I like keeping my scenarios and steps in one file until the feature becomes sufficiently big that it warrants extra organizational consideration.

These reasons are more-or-less the same as those given by Evan Light, who recently published Coulda, which is his solution for avoiding the cuke. What sets Spectie apart from Coulda is its reliance on and integration with RSpec. The Spectie 'Feature' statement has the same behavior as an RSpec 'describe' statement, and the 'Scenario' statement is the same as the RSpec 'example' and 'it' statements. By building on RSpec, Spectie can take advantage of the contextual nesting provided by RSpec, and rely on RSpec to provide the BDD-style syntax within what I've been calling a scenario statement (the words after the Given/When/Thens). Coulda is built directly on Test::Unit. I'm a firm believer in code reuse, and RSpec is the de facto standard for writing BDD-style tests. Spectie, then, is a feature-driven skin on top of RSpec for writing BDD-style integration tests. To me, it only makes sense to do things that way; as RSpec evolves, so will Spectie.

Testing on High: Bottom-up versus Top-down Test-driven Development 40

Posted by ryan Mon, 19 Nov 2007 02:13:21 GMT

I recently talked to a number of Rails developers about their general approach to testing some new functionality they're about to code. I asked these developers if they found it to be more useful to start testing from the bottom-up or top-down. I suggested to them that, since Rails uses the MVC pattern, it's easy to think of the view, or user interface, as the "top", and the model as the "bottom". Surprisingly, nearly every developer that I asked this question of answered that they prefer to start from the bottom, or model, and test upwards. Nearly every one! I expected that I'd get a much more mixed response than I have. In fact, I think that the correct place to start testing is precisely at the highest level possible, to reduce the risk of building software based on incorrect assumptions of how best to solve a user requirement.

Bottom-up Testing

Bottom-up testing implies bottom-up design in TDD. In bottom-up design, a developer would probably consider the high-level objectives and break them up into manageable components that interact with each other to provide the desired functionality. The developer thinks about how each component will be used by its client components, and tests accordingly.

The problem with the bottom-up approach is that it's difficult to really know how a component needs to be used by its clients until the clients are implemented. To consider how the clients will be implemented, the developer must also think about how those clients will be used by their clients. This thought process continues until we reach the summit of our mighty design! Hopefully, when the developer is done pondering, they can write a suite of tests for a component which directly solves the needs of its client components. In my experience, however, this is rarely the case. What really happens is that the lower-level components tend either to do too much, too little, or the right amount in a way that is awkward or complicated to make use of.

The advantage of bottom-up testing is that, since we're starting with the most basic, fundamental components, we guarantee that we'll have some working software fairly quickly. However, since the software being written may not be closely associated with the high-level user requirements, it may not produce results that are necessarily valuable to the user. A simple client could quickly be written which demonstrates how the components work to the user, but that's besides the point unless the application being developed is a simple application. In such a case, the bottom-level of components are probably close enough to the top-level ones that there is little risk involved in choosing either the bottom-up or top-down approach.

Unless you're writing a small application, the code is probably going to have to support unforeseen use cases. When this comes as a result of ungrounded assumptions about the software that's already been written, this can mean a lot of rework. I can tell you from experience, once you realize that your lower-level components don't fit the bill for the higher levels in the system, it can be quite a chore to go back and fix, remove, or replace all of that unnecessary or incorrect code.

Top-down Testing

Top-down testing implies top-down design in TDD. Following the top-down approach, the developer will pick the highest level of the system to be tested; that is to say, the part of the system that has the closest correlation to the user requirements. This approach is sometimes referred to as Behavior Driven Development. Whatever it's called, the point is that you test the most critical parts of the application first.

Since software is often written for human users, the most critical parts usually involve the front-end as it relates to the value being provided by the system being developed. When testing from the top-down, the effort is the inverse of bottom-up testing: Instead of spending a lot of time thinking about how the components to be developed will be used by other components to be developed, the focus is on how the user needs to interact with the system. Testing involves proving that the system supports the required usability. For an application with a graphical front-end, this might involve testing for a minimal version of that front-end.

The disadvantage of top-down testing is that you can end up with a lot of stubbed or mocked code that you then have to go back and implement. This means it might take longer before you have software that actually does something besides pass tests. However, there are ways that you can minimize this sort of recursive development problem.

One way to minimize the time between starting development of a feature and demonstrating functionality that is valuable to the user is to focus on a thin slice of the overall architectural pie of the application. For example, there may be a number of views that need to be implemented before the system provides some major piece of functionality. However, the developer can focus on one view at a time, or one part of the view. That way, the number of components that need to be implemented before the system does something useful is small; ideally, one component in each architectural layer that I need build out, and often times only a part of the overall functionality of each component.

Another way to minimize the amount of time before the system does something useful is to code a small bit of functionality without worrying about breaking the problem up into classes until you have some tested, working code to analyze. You can then use established methods for refactoring to bring the code to an acceptable level of quality.

The advantage of top-down testing is that you write functionality that solves the most critical functionality first. This generally means starting development at a high level. When the system eventually does something besides pass tests, what it does will provide value to its users. Additionally, because development starts at a high level, the code that is written is based on the current understanding of the problem, and not on assumptions. This guarantees that the tests and code that are written are not superfluous.

Conclusion

The challenge with top-down testing is that you must be highly disciplined to ensure that the code you write is being refactored and is properly evolving into a cohesive domain model for the application. This is compared with bottom-up testing, where you start with the domain model and build your system around it. Either way, you're going to be refactoring code. The difference is in where the time in refactoring is spent. In my experience, when doing bottom-up testing, more time is spent correcting incorrect assumptions about how the domain model will be used than on actually improving code that already works to solve the user requirements. In order to avoid making assumptions about the code being written, it must be written at the level that is closest to providing actual value to the end-user. In so doing, the developer focuses on continuous refinement of code that already provides value, as opposed to speculative design and development.