module TimeZoneTestHelpers
  def with_tz_default(tz = nil)
    old_tz = Time.zone
    Time.zone = tz
    yield
  ensure
    Time.zone = old_tz
  end

  def with_env_tz(new_tz = 'US/Eastern')
    old_tz, ENV['TZ'] = ENV['TZ'], new_tz
    yield
  ensure
    old_tz ? ENV['TZ'] = old_tz : ENV.delete('TZ')
  end
end