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A walk through of test-driven development with shoulda


I’m not sure if you’ve heard, but shoulda makes test-driven development really simple.

Last week’s boston.rb focused on testing, where we split up into two groups. One group worked on adding a test suite to an app that had no tests, and my group was using test-driven development for adding new features to the boston.rb website.

I figured I’d do recap how we used TDD that night.

shoulda-generators, a quick plug

One thing I’m going to omit from the walkthrough is that a chunk of time was spent converting the scaffold-generated test from test-unit to shoulda, and from erb to haml. While it was a worthwhile detour for some present, it was a little annoying. If only there were shoulda and haml generators, I say!

Struck awake by inspiration at 5am the next day, I took fate into my own hands

BEHOLD!

It is available as a plugin for now, but I’ll try to gemify it sometime.

While we didn’t have the luxury of these generators at the time, I’m going to use them now for the sake of this writeup.

The new feature: Places

Before we start, let’s just make sure the tests work… alright, good.

We want to add functionality for ‘places.’ A Place is somewhere in the area that’s somehow connected to Ruby: a business using it, a venue for a meeting, an incubator, things like that.

A Place probably has:

  • A name
  • An address
  • A description

Let’s generate the scaffold:

$ script/generate shoulda_scaffold place name:string address:string description:text
      exists  app/models/
      exists  app/controllers/
      exists  app/helpers/
      create  app/views/places
      exists  app/views/layouts/
      exists  test/functional/
      exists  test/unit/
      create  public/stylesheets/blueprint
      create  app/views/places/index.html.haml
      create  app/views/places/show.html.haml
      create  app/views/places/new.html.haml
      create  app/views/places/edit.html.haml
      create  app/views/places/_form.html.haml
      create  app/views/layouts/places.html.haml
      create  public/stylesheets/blueprint/print.css
      create  public/stylesheets/blueprint/screen.css
      create  public/stylesheets/blueprint/ie.css
      create  app/controllers/places_controller.rb
      create  test/functional/places_controller_test.rb
      create  app/helpers/places_helper.rb
       route  map.resources :places
  dependency  shoulda_model
      exists    app/models/
      exists    test/unit/
      create    test/factories/
      create    app/models/place.rb
      create    test/unit/place_test.rb
      create    test/factories/place.rb
      create    db/migrate
      create    db/migrate/20080620011343_create_places.rb

Let’s try the tests again.

$ rake test
(in /Users/nichoj/Projects/bostonrb)
You have 1 pending migrations:
  20080620011343 CreatePlaces
Run "rake db:migrate" to update your database then try again.

Whoops, need to migrate first.

$ rake db:migrate
(in /Users/nichoj/Projects/bostonrb)
== 20080620011343 CreatePlaces: migrating =====================================
-- create_table(:places)
   -> 0.0171s
==
$ rake test
(in /Users/nichoj/Projects/bostonrb)
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/Library/Ruby/Gems/1.8/gems/rake-0.8.1/lib/rake/rake_test_loader.rb" "test/unit/place_test.rb" 
Loaded suite /Library/Ruby/Gems/1.8/gems/rake-0.8.1/lib/rake/rake_test_loader
Started
...
Finished in 0.147509 seconds.

3 tests, 3 assertions, 0 failures, 0 errors
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/Library/Ruby/Gems/1.8/gems/rake-0.8.1/lib/rake/rake_test_loader.rb" "test/functional/places_controller_test.rb" 
Loaded suite /Library/Ruby/Gems/1.8/gems/rake-0.8.1/lib/rake/rake_test_loader
Started
...........
Finished in 0.293275 seconds.

11 tests, 14 assertions, 0 failures, 0 errors
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -Ilib:test "/Library/Ruby/Gems/1.8/gems/rake-0.8.1/lib/rake/rake_test_loader.rb"

Good so far.

Now what do we want to do with the place? Those attributes should be required. Open the test, and see what we have so far:

class PlaceTest < ActiveSupport::TestCase
  should_have_db_column :name
  should_have_db_column :address
  should_have_db_column :description
end

Oh, cool. The generated test already has a few shoulds in there. Now we want to add should_require_attributes.

class PlaceTest < ActiveSupport::TestCase
  should_have_db_column :name
  should_have_db_column :address
  should_have_db_column :description
  should_require_attributes :name, :address, :description
end

And let’s see how this does

$ ruby test/unit/place_test.rb
Loaded suite test/unit/place_test
Started
...FFF
Finished in 0.154072 seconds.

  1) Failure:
test: Place should require address to be set. (PlaceTest)
    [/Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/active_record_helpers.rb:41:in `__bind_1213925922_190232'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `call'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `test: Place should require address to be set. '
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
Place does not require address.
<false> is not true.

  2) Failure:
test: Place should require description to be set. (PlaceTest)
    [/Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/active_record_helpers.rb:41:in `__bind_1213925922_194386'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `call'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `test: Place should require description to be set. '
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
Place does not require description.
<false> is not true.

  3) Failure:
test: Place should require name to be set. (PlaceTest)
    [/Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/active_record_helpers.rb:41:in `__bind_1213925922_196154'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `call'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `test: Place should require name to be set. '
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
Place does not require name.
<false> is not true.

6 tests, 6 assertions, 3 failures, 0 errors

Ok, this is to be expected. We didn’t actually validate_presence_of the fields. Let’s do that now:

class Place &lt; ActiveRecord::Base
  validates_presence_of :name
  validates_presence_of :address
  validates_presence_of :description
end

If we try it again

$ ruby test/unit/place_test.rb
Loaded suite test/unit/place_test
Started
......
Finished in 0.153653 seconds.

6 tests, 12 assertions, 0 failures, 0 errors

Test-driven, wooo!!! I think this is good enough to commit.

Relating places and events

We already have an Event model, so I figure a Place should be able to have events, and event would have could be at a particular place. Shall we test it?

class PlaceTest < ActiveSupport::TestCase
  # omitted...
  should_have_many :events
end

We get a failure though:

  1) Failure:
test: Place should have many events. (PlaceTest)
    [/Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/active_record_helpers.rb:378:in `__bind_1213931312_854475'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `call'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `test: Place should have many events. '
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
Place does not have any relationship to events.
<nil> is not true.

Now we add the has_many to Place. But we still have a failure!

 1) Failure:
test: Place should have many events. (PlaceTest)
    [/Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/active_record_helpers.rb:405:in `__bind_1213931441_769681'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `call'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `test: Place should have many events. '
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
Event does not have a place_id foreign key.
<false> is not true.

Oh, probably should migrate something.

$ script/generate migration place_event_relationship
      exists  db/migrate
      create  db/migrate/20080620031448_place_event_relationship.rb

And we make it look like:

class PlaceEventRelationship &lt; ActiveRecord::Migration
  def self.up
    add_column :events, :place_id, :integer
  end

  def self.down
    remove_column :events, :place_id
  end
end

Do a rake db:migrate db:test:prepare, and we’re ready to run it again. Wait for it… wait for it

$ ruby test/unit/place_test.rb 
Loaded suite test/unit/place_test
Started
.......
Finished in 0.159728 seconds.

7 tests, 15 assertions, 0 failures, 0 errors

Let’s add a test for the other side of the relationship:

class EventTest < ActiveSupport::TestCase
  # ... snip ...
  should_belong_to :place
end

Failures, as expected.

 1) Failure:
test: Event should belong_to place. (EventTest)
    [/Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/active_record_helpers.rb:476:in `__bind_1213933933_768823'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `call'
     /Users/nichoj/Projects/bostonrb/vendor/plugins/shoulda/lib/shoulda/gem/shoulda.rb:191:in `test: Event should belong_to place. '
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `__send__'
     /Library/Ruby/Gems/1.8/gems/activesupport-2.1.0/lib/active_support/testing/setup_and_teardown.rb:67:in `run']:
Event does not have any relationship to place.
<nil> is not true.

And now we actually implement it

class Event < ActiveRecord::Base
  belongs_to :place
end

And guess what? They pass. We win at things that are winnable, like TDD.

Summary

These have been pretty trivial examples, but it demonstrates how to roll with TDD.

  • Write a test
  • See it fail
  • Write code
  • See the test pass
  • Repeat

It also demonstrates how shoulda lets tersely test things that can be written tersely with Rails.

Update

The repository was renamed shoulda_generator. It is also now installable as a gem:

$ gem sources -a http://gems.github.com
$ sudo gem install technicalpickles-shoulda_generator
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