Cucumber Backgrounder

Or: How I Learned to Stop Worrying and Love Testing

Introduction

This discussion deals principally with the initial set up and use of cucumber features in a Ruby on Rails (RoR) Project. Discussion of Behaviour Driven (BDD), Test Driven (TDD), and Panic Driven Development (SNAFU) can be found elsewhere. Details regarding installing the Cucumber gem and its recommended support tools for RoR are found at Ruby on Rails.

Where to Start?

Given that you have installed the gem called "Cucumber"
  And you have generated a RoR project called "MyProject"
  And your session's working directory is called "MyProject"

When you run "script/generate cucumber"

Then you will create a sub-directory called "features"

The foregoing is written in the style of the feature statements that make up the user interface to cucumber testing. We will return to that topic later. For the moment we deal with the logical arrangement of cucumber files within the context of a RoR project.

The root level of the archetypal RoR project directory tree looks like this:

MyProject
|-- README
|-- Rakefile
|-- app
|-- config
|-- db
|-- doc
|-- lib
|-- log
|-- public
|-- script
|-- test
|-- tmp
`-- vendor

Running script/generate cucumber adds this layout to the existing structure:

|-- features
|   |-- step_definitions
|   |   `-- webrat_steps.rb
|   `-- support
|       `-- env.rb

We are now ready to begin testing with cucumber.

Where do I put Tests?

Cucumber divides testing into two parts, the outward facing features and the inward facing steps. As discussed elsewhere, Feature Introduction are descriptions of desired behaviour under predefined conditions and following upon specific events. They are typically used in conjunction with end-user input, and in some cases, may be entirely under end-user (in the form of a domain expert) control. Feature files are given the extension .feature.

Step Organisation, on the other hand, are ruby (.rb) files that contain matchers, snippets of text from the feature files, and blocks of ruby and rails code together with assertions from whatever test system you have installed. Given that cucumber evolved out of RSpec stories it is assumed in the cucumber generator that rspec is available, as is evidenced in the default contents of features/support/env.rb:

# Sets up the Rails environment for Cucumber
ENV["RAILS_ENV"] = "test"
require File.expand_path(File.dirname(__FILE__) + '/../../config/environment')
require 'cucumber/rails/world'
Cucumber::Rails.use_transactional_fixtures

# Comment out the next line if you're not using 
# RSpec's matchers (should / should_not) in your steps.
require 'cucumber/rails/rspec'

You are not limited to this however. If you choose to use Rails built-in TestUnit, or any other testing suite, then you may do that by extending the cucumber working environment as explained in Using Test::Unit.

The default layout of the features directory is fairly shallow. However, cucumber is programmed with the flexibility to support a much more expressive directory structure. For instance:

|-- features
|   |-- entities
|   |   |-- entity.feature
|   |   `-- step_definitions
|   |       |-- anything.rb
|   |       `-- entity_steps.rb
|   |-- locations
|   |   |-- location.feature
|   |   `-- step_definitions
|   |       `-- location_steps.rb
|   |-- sites
|   |   `-- step_definitions
|   |-- step_definitions
|   |   `-- webrat_steps.rb
|   `-- support
|       `-- env.rb

In this case the bland initial setup has been divided into sub-directories informed by model-centric testing. However this could equally well have been broken up in to model/controller/view hierarchies:

|-- features
|   |-- models
|   |   |-- entities
|   |   |   |-- entity.feature
|   |   |   `-- step_definitions
|   |   |       |-- anything.rb
|   |   |       `-- entity_steps.rb
|   |-- views
|   |   |   |-- entity_new
|   |   |   `-- step_definitions
|   |   |       `-- entity_new_steps.rb
|   |-- step_definitions
|   |   `-- webrat_steps.rb
|   `-- support
|       `-- env.rb

Consider, however, that the cucumber feature generator will place the files it produces in conformance with the default layout. It is well to be aware that, regardless of the directory structure chosen, cucumber effectively flattens the test directory when running tests. By this I mean that anything ending in .rb under the start point for a cucumber feature run is searched for feature matches. So that a step contained in features/models/entities/step_definitions/anything.rb can be used in a feature file contained in features/views/entity_new. It is also worth noting that step files can be called anything so long as they end in .rb.

How do I Write Tests?

Detailed discussion of feature writing and step construction are provided elsewhere (and I will provide links when I get around to it). None-the-less, a brief outline is provided here. Perhaps the easiest thing to do is to use cucumber’s built-in generator to create a feature scaffold and modify it.

script/generate feature Frooble name color description
      exists  features/step_definitions
      create  features/manage_froobles.feature
      create  features/step_definitions/frooble_steps.rb

A Feature is typically contained in its own file (ending in .feature). Each Feature consists of multiple Scenarios. Each Scenario consists of three sections, Given, When and Then. Each section consists of one or more clauses that are used to match test steps. The conventional arrangement is:

Feature: Some terse yet descriptive text
In order to/that <some business value>
A/an <some actor>
Should <some beneficial outcome>
To Increase Revenue | Reduce Costs | Protect Revenue  

  Scenario:   Some determinable business situation
      Given some condition to meet
         And some other condition to meet
       When some action by the actor
         And some other action
         And yet another action
       Then some testable outcome is achieved
         And something else we can check happens too

  Scenario:  A different situation
      ...

For cucumber the key words use here are Feature, Scenario, Given, When, Then, and And. Feature is used to provide identification of the test group when results are reported. Scenario is used in the same fashion. Given, When, Then, and And are cucumber methods that take as their argument the string that follows. These are the steps that cucumber will report as passing, failing or pending based on the results of the corresponding step matchers in the step_definitions files. These methods are also all equivalent:

      def Given(name)
        create_step('Given', name, *caller[0].split(':')[1].to_i)
      end
def When(name)
create_step(‘When’, name, *caller0.split(‘:’)1.to_i)
end
def Then(name)
create_step(‘Then’, name, *caller0.split(‘:’)1.to_i)
end
def And(name)
create_step(‘And’, name, *caller0.split(‘:’)1.to_i)
end

The string from each one of these method is compared against the matchers contained in the step.rb files. A step matcher looks much like this:

Given /there are (\d+) froobles/ do |n|
  Frooble.transaction do
    Frooble.destroy_all
    n.to_i.times do |n|
      Frooble.create! :name => "Frooble #{n}"
    end
  end
end

The significant thing here is that the method (Given) takes as its argument a regexp bounded by /. For example, in the features given above we had the statement: And some other action. This could be matched by any of the following step matchers in any step file under the features directory.

Given /some other action/ do
When /some (.*) action/ do |match|
Then /(*.) other action/ do |match|
And /some other act.*/ do 
Given /(.*) other (.*)/ do |first,second|

Which raise an interesting point. If you had all of these matchers defined somewhere then cucumber would tell you that it found multiple matches for a single feature step and force you to distinguish them.

Note that you are not required to use a matched subpattern, (.* ), in the following block.

It is considered better form by some to surround with double quotation marks, ", elements in the feature step clauses that are meant to be taken as values. This is only a convention and one not followed by many. However, if you choose to follow this road then you must adjust your step files accordingly. For example:

Given Some determinable "business" situation

Given /determinable "(.*)" situation/ do |s|

Finally, you can have steps call steps. For example:

And /some "(.*)" action/  do |a|
   ...
end

When /in an invoiced non-shipped situation/ do
  Given "some \"invoiced\" action" 
  Then "some \"non-shipped\" action"
  ...
end

Worthy of note is that, inside the step files, one must enclose the arguments to the Given/When/Then/And methods with a string delimiter. Because of this, if you have adopted the practice of demarcating values in the step matchers with double quote marks then you must escape them in the equivalent step strings. You should also be cautious not to include the quote marks in the value matchers, “(.)” is not the same as (.*). If you use quotes in the feature files and do not account for them in your matchers then you will get variables that contain leading and trailing quotes as part of their values.

Scenario: Quotes surround value elelments
  Given some "required" action

# step_definitions
And /some (.*) action/ do |a|
  a => "required"

And /some "(.*)" action/ do |a|
  a => required

What Way do I Run the Tests?

Begin with

rake db:migrate
rake db:test:prepare

Testing with cucumber can be performed in several fashions. Be aware that Rake features, cucumber features, and autotest with ENV AUTOFEATURE=true do not necessarily produce the same results given the same tests.

Running rake features from the command line provides the easiest and most reliable method to run cucumber tests. The rake script provided with cucumber performs much of the background magic required to get the test database and requisite libraries properly loaded.

Running cucumber directly from the command line requires the creation of a cucumber.yml file in the project root directory, even if that file remains empty. When cucumber is run from the command line it is usually necessary to provide both the directory name containing the root directory of the tree containing feature files and the directory name containing references to the necessary library files. In the typical project cucumber features -r features will normally suffice.

Finally, running autotest with the environment variable AUTOFEATURE=true will run ALL tests, including those in /test. It will also load all test fixtures and this may leave the database in an indefinite state when cucumber features begin to run. It is wise therefore, to write cucumber steps so that they do not depend upon an empty database or themselves place the database in the requisite state.

Anything Else?

For those of you that have used growl or snarl to provide desktop notifiers from autotest be advised that as of this writing cucumber did not hook into the :red :green notifier capability of autotest. So, no popups when a test fails.