example2.rb

#! /usr/bin/env ruby

require 'rubygems'
require 'sequel'

# class TestDatabase
#   def up; [nil, nil, nil]; end # (blah blah blah)
#   def down; [nil, nil, nil]; end
# end
# 
# class TestSetup < Sequel::Migration
#   def up 
#     create_table! :test do
#       primary_key :id
#       foreign_key :parent_id, :test
#       String  :name, :null => false
#     end unless table_exists? :test
#     # Look!  Here, the Test class has not yet been defined!  O_o
#     Test.set_dataset :test
#     Test.plugin :class_table_inheritance, :key => :object_type
#   end
# 
#   def down; drop_table :test if table_exists? :test; end
# end

# Setup schema correctly

TestDatabase.down       # Placing the migration code in the main Object like this requires
TestDatabase.up         # that the classes defining TestDatabase and TestSetup be defined 
TestSetup.down          # within the main Object namespace previous to these invocations.
TestSetup.up            # This means that every time I wish to re-apply a plugin or dataset, 
                        # it must be done _outside_ these migration helpers.  This thwarts  
                        # my intention to keep the code for the db+schema setup/tear-down in
                        # one reusable place, since if it remained in the TestDatabase or
                        # TestSetup classes (which, remember, have been defined prior to the 
                        # Test model), the Test model class would not yet exist.

# Define models

class Test < Sequel::Model
end

# Test code

class TestSomeDatabaseRoutines
  def setup
    # Rebuild schema
    TestDatabase.down
    TestDatabase.up
    TestSetup.down
    TestSetup.up
  end

  def test_create
    a = Test.create(:name => 'Hello!')
    assert(a != nil and a.name == 'Hello!')
  end
end