rails--rails/activesupport/test/time_zone_test_helpers.rb

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

  def with_preserve_timezone(value)
    old_preserve_tz = ActiveSupport.to_time_preserves_timezone
    ActiveSupport.to_time_preserves_timezone = value
    yield
  ensure
    ActiveSupport.to_time_preserves_timezone = old_preserve_tz
  end
end