mongoid complex query

mongoid_query.rb

require 'mongoid'
require 'fabrication'

Mongoid::Config.load_configuration({
  sessions: {
    default: {
      hosts: ['localhost:27017'],
      database: 'local'
    }
  }
})

class MyModel

  include Mongoid::Document
  field :enabled, type: Boolean
  field :start_date, type: DateTime
  field :end_date, type: DateTime

  def self.active
    start_date = Date.today
    end_date = Date.tomorrow
    where(
      enabled: true,
      :$or => [
        {:start_date.lte => start_date, :end_date.gte => end_date},
        {:start_date => nil, :end_date.gte => end_date},
        {:start_date.lte => start_date, :end_date => nil},
        {:start_date => nil, :end_date => nil},
      ]
    )
  end

  def self.buggy_active
    start_date = Date.today
    end_date = Date.tomorrow
    where(
      :$and => [
        enabled: true,
        :$or => [
          { start_date: nil },
          { :start_date.lte => start_date }
        ],
        :$or => [
          { end_date: nil },
          { :end_date.gte => end_date }
        ]
      ]
    )
  end

end

Fabricator(:model, class_name: MyModel)
Fabricator(:active_model, from: :model) do
  enabled true
end

describe '.active' do

  let!(:disabled){ Fabricate(:model, enabled: false, name: 'disabled') }
  let!(:enabled_without_date){ Fabricate(:active_model, name: 'enabled_without_date') }
  let!(:past){ Fabricate(:active_model, start_date: 1.week.ago, end_date: Date.yesterday, name: 'past') }
  let!(:current){ Fabricate(:active_model, start_date: Date.today, end_date: Date.tomorrow, name: 'current') }
  let!(:future){ Fabricate(:active_model, start_date: Date.tomorrow, end_date: 1.week.from_now, name: 'future') }

  after :each do
    Moped::Session.new(['localhost:27017']).with(database: 'local') do |_session|
      _session.drop
    end
  end

  it 'returns only enabled and within the current time' do
    MyModel.count.should == 5
    models = MyModel.active.to_a
    models.should_not be_empty
    models.should_not include disabled
    models.should_not include future
    models.should_not include past
    models.should include enabled_without_date
    models.should include current
  end

end