The default task for loading fixtures, rake load_fixtures, appears to load the fixture data in alphabetical order. If you have foreign key or other constraints, it may be impossible to load the fixtures into the database.

The rake task below searches for a file called test/ordered_fixtures.rb and loads that file. The file contains code that sets an environment variable specifying the load order for fixtures.

ENV["FIXTURE_ORDER"] = 
  %w( entities interaction_sources interaction_devices payments 
      interactions accounts employments enrollments payables 
      receivables tenures wards ).join(' ')

The lib/tasks/fixtures.rake (rake load_fixtures_ordered) task first loads all fixtures specified via ordered_fixtures, and then loads all other fixtures not specified as being ordered so it should work for you even if you do not create an ordered_fixtures file.

require File.expand_path(File.dirname(__FILE__) + "/../../config/environment")
require File.expand_path(File.dirname(__FILE__) + "/../../test/ordered_fixtures")

ENV["FIXTURE_ORDER"] ||= ""

desc "Load fixtures into #{ENV['RAILS_ENV']} database"
task :load_fixtures_ordered => :environment do
  require 'active_record/fixtures'  
  ordered_fixtures = Hash.new
  ENV["FIXTURE_ORDER"].split.each { |fx| ordered_fixtures[fx] = nil }
  other_fixtures = Dir.glob(File.join(RAILS_ROOT, 'test', 'fixtures', '*.{yml,csv}')).collect { |file| File.basename(file, '.*') }.reject {|fx| ordered_fixtures.key? fx }
  ActiveRecord::Base.establish_connection(ENV['RAILS_ENV'])
  (ordered_fixtures.keys + other_fixtures).each do |fixture|
    Fixtures.create_fixtures('test/fixtures',  fixture)
  end unless :environment == 'production' 
  # You really don't want to load your *fixtures* 
  # into your production database, do you?  
end

The code may not be the best but it Works For Me.