Working With Rails

Fixture Scenarios Builder

This plugin is an add-on to the FixtureScenarios plugin by Tom Preston-Werner. FixtureScenarios is required for this plugin to work.

FixtureScenarios Info: http://code.google.com/p/fixture-scenarios/ SVN : http://fixture-scenarios.googlecode.com/svn/trunk/fixture_scenarios

This plugin Info: http://errtheblog.com/post/7708 SVN : svn://errtheblog.com/svn/plugins/fixture_scenarios_builder Bugs: http://err.lighthouseapp.com/projects/466-plugins/tickets/new

The Setup

You may, from time to time, wish to build your fixtures entirely in Ruby. Doing so has its advantages, such as automatically created join tables and default attributes. YAML files, however, bring with them some real nice features in Rails which are difficult to abandon: transactional fixtures, table_name(:key) helpers, and auto-clearing between tests. How does one get the best of both worlds?

The Download

Using the scenario method within scenarios.rb file, FixtureScenariosBuilder can create your YAML fixture scenarios automatically at run time from Ruby-created fixtures.

Create a scenarios.rb file and place it in the root “fixtures” directory:

[RAILS_ROOT]
+-test/
  +-fixtures/
    +-scenarios.rb

Now build your scenarios in this file, wrapping scenarios in the scenario method and providing it with the name of your scenario. A brief example of a complete scenarios.rb file:

scenario :banned_users do
  %w( Tom Chris Kevin ).each_with_index do |user, index|
    User.create(:name => user, :banned => index.odd?)
  end
end

Assuming banned is a boolean field, this will create for us (when our tests are first run) the following:

[RAILS_ROOT]
+-test/
  +-fixtures/
    +-banned_users/
      +-users.yml

Our generated users.yml file will look something like this:

chris: 
  name: Chris
  id: "2" 
  banned: "1" 
  updated_at: 2007-05-09 09:08:04
  created_at: 2007-05-09 09:08:04
kevin: 
  name: Kevin
  id: "3" 
  banned: "0" 
  updated_at: 2007-05-09 09:08:04
  created_at: 2007-05-09 09:08:04
tom: 
  name: Tom
  id: "1" 
  banned: "0" 
  updated_at: 2007-05-09 09:08:04
  created_at: 2007-05-09 09:08:04

Notice how the keys correspond to the user names. FixtureScenariosBuilder will try, to an extent, to guess the name of your key. If it can’t figure it out, keys will be the standard user_001, user_002, etc format.

Thanks to Paul Cantrell’s handywork, custom key names are supported. Simply use the name method:

scenario :foo do
  name "small_red_widget", Widget.create(:size => 'small', :color => 'red')
  name "big_blue_widget",  Widget.create(:size => 'big',   :color => 'blue')
end

Another option is to assign your records to instance variables, then call names_from_ivars at the conclusion of your scenario block.

scenario :foo do
  @small_red_widget = Widget.create(:size => 'small', :color => 'red')
  @big_blue_widget  = Widget.create(:size => 'big',   :color => 'blue')
end

names_from_ivars!

The above produces the following YAML:

small_red_widget:
  size: small
  color: red
  updated_at: 2007-12-27 10:09:05
  created_at: 2007-12-27 10:09:05
big_blue_widget:
  size: big
  color: blue
  updated_at: 2007-12-27 10:19:23
  created_at: 2007-12-27 10:19:23

On subsequent test runs this YAML file will not be needlessly re-created. YAML files will only be re-generated when the scenarios.rb file is modified.

If you for some reason need to force your scenarios to rebuild, pass in the REBUILD_FIXTURES environment variables:

$ rake test:units REBUILD_FIXTURES=true

Scenarios can also be nested using the familiar Rake-style dependency declaration.

scenario :users do
  %w( Tom Chris ).each do |user|
    User.create(:name => user)
  end
end

scenario :banned_users => :users do
  User.create(:name => 'Kevin', :banned => true)
end

Rake

FixtureScenariosBuilder comes with one Rake task, `db:scenario:build' -- use it to attempt to build your scenarios on demand.

Bugs!

Please report bugs here: http://err.lighthouseapp.com/projects/466-plugins/tickets

Chris Wanstrath => chris[at]ozmm[dot]org

NOTE: This description has been extracted from the Plugin README and so the formatting may need updating to make browser friendly