```ruby
require 'logger'

module Experimental
  class Loader
    def initialize(options = {})
      @logger = options[:logger] || Logger.new('/dev/null')
    end

    attr_reader :logger

    def sync
      logger.info "Synchronizing experiments..."

      Experimental::Experiment.transaction do
        active = Experimental.experiment_data.map do |name, attributes|
          experiment = Experimental::Experiment.find_or_initialize_by_name(name)

          unstarted = attributes.delete('unstarted')
          defaults = {'num_buckets' => nil, 'notes' => nil, 'population' => nil}
          experiment.assign_attributes(defaults.merge(attributes))
          if unstarted
            experiment.start_date = nil
          else
            experiment.start_date ||= Time.current
          end

          logger.info "  * #{experiment.id ? 'updating' : 'creating'} #{name}"
          experiment.tap(&:save!)
        end

        scope = Experimental::Experiment.in_code
        scope = scope.where('id NOT IN (?)', active.map(&:id)) unless active.empty?
        scope.find_each do |experiment|
          next if experiment.admin?
          logger.info "  * removing #{experiment.name}"
          experiment.remove
        end
      end

      logger.info "Done."
    end
  end
end
```

Fix spec failures under Rails 4.1.
user
```ruby
require 'logger'

module Experimental
  class Loader
    def initialize(options = {})
      @logger = options[:logger] || Logger.new('/dev/null')
    end

    attr_reader :logger

    def sync
      logger.info "Synchronizing experiments..."

      Experimental::Experiment.transaction do
        active = Experimental.experiment_data.map do |name, attributes|
          experiment = Experimental::Experiment.where(name: name).first_or_initialize

          unstarted = attributes.delete('unstarted')
          defaults = {'num_buckets' => nil, 'notes' => nil, 'population' => nil}
          experiment.assign_attributes(defaults.merge(attributes))
          if unstarted
            experiment.start_date = nil
          else
            experiment.start_date ||= Time.current
          end

          logger.info "  * #{experiment.id ? 'updating' : 'creating'} #{name}"
          experiment.tap(&:save!)
        end

        scope = Experimental::Experiment.in_code
        scope = scope.where('id NOT IN (?)', active.map(&:id)) unless active.empty?
        scope.find_each do |experiment|
          next if experiment.admin?
          logger.info "  * removing #{experiment.name}"
          experiment.remove
        end
      end

      logger.info "Done."
    end
  end
end
```
assistant