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Cucumber: The Latest in Ruby Testing

By Mike Gunderloy / November 19, 2008

Testing is a firmly ingrained part of the Ruby culture: you probably ran across Test::Unit not long after you first started writing Ruby code (though it wouldn't be surprising if you ignored it for a while). But it hasn't been a static part of Ruby - we've seen the simple availability of tests evolve into test-driven development (TDD) that in turn gave rise to behavior-driven development (BDD). Along the way, Ruby has spawned a variety of testing tools and frameworks. The latest, Aslak Hellesoy's Cucumber, is the latest addition to the RSpec family of tools.

Cucumber is designed to allow you to execute feature documentation written in plain text (often known as "stories"). I've been experimenting with it as a replacement for integration tests in Rails. With Cucumber, you can write tests that look like this:

Scenario: See all vendors
    Given I am logged in as a user in the administrator role
    And There are 3 vendors
    When I go to the manage vendors page
    Then I should see the first 3 vendor names

With Cucumber, that it an executable specification that you can discuss with the customer and then use to verify the correct behavior of tests. Behind the scenes, you make it work by writing "steps," which are regex matchers that execute Ruby code. Here's one of the steps for that scenario:

Given /there are (d+) vendors/i do |n|
  Vendor.transaction do
    n.to_i.times do |n|
      Factory.create(:vendor, :business_name => "Vendor #{n}")

Ideally, you'll do this all in true BDD fashion: write the Cucumber features first, watch them fail, implement code to make them pass (with lower-level tests written with RSpec or Test::Unit), and repeat.

Cucumber is under rapid development, but it's already a useful part of my testing toolbox. In addition to integrating with RSpec and Rails, it works with Merb, Sinatra, and the Webrat web-testing framework (as well as, of course, pure Ruby projects). It also has translations into 20 languages and the ability to run FIT-style tabular tests. If you're looking for a higher level of abstraction in your tests, it's definitely worth checking out.

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  1. Daniel Berger says:

    Brandon Keepers gave a talk on Cucumber at the Great Lakes Ruby Bash 2008. In case anyone is interested his slides are available online at:

  2. Peter Cooper says:

    Awesome, thanks Daniel!

  3. Mark Wilden says:

    "you probably ran across Test::Unit not long after you first started writing Ruby code (though it wouldn't be surprising if you ignored it for a while)"

    Then there are those of us who've been TDDing for 10 years and came to Ruby and RoR precisely *because* of its support for testing.

  4. Bart ten Brinke says:

    Does cucumber do the same thing as ? Only without the selenium integration? Or am I missing the point here?

  5. Kevin Mears says:

    I came across a great write up of the nitty gritty of getting started on "Craig's Site":

  6. rue says:

    COBOL, is that you? :)

    I am a bit apprehensive of this direction.. but it would not be the first time I turned out to be wrong.

  7. Chad Humphries says:

    Cucumber also works well with test/spec and test::unit as well.

  8. Bruce Williams says:

    It seems to work well with pretty much any testing framework (I've been using it with matchy, as well). It's a shame it has [what seems to be an unnecessary] gem runtime dependency on rspec and that the documentation thus far seems skewed in using it in that way.

  9. anonymouse says:

    @rue: No, COBOL had only a few predetermined templates like "ADD x TO y GIVING z". This language lets you write your own templates (and define your own routines to implement the templates). Not even in the same class.

  10. Jeremy Jarvis says:

    My colleague Rahoul has also just posted a step by step intro to using Rspec, Cucumber and Stories...

  11. Aslak Helles√ły says:

    Cucumber no longer depends on RSpec, and I have added an example showing how to use plain Test::Unit assertions inside step definitions.

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