Testing Elixir: test code typo (page 70, beta 4)

There’s no RollingAverageMeasurements.add_element/1 variant. The two calls to RollingAverageMeasurements.add_element should either be piped with measurements as the target, or add measurements as the first parameter, e.g.,

measurements =
  measurements
  |> RollingAverageMeasurements.add_element(1)
  |> RollingAverageMeasurements.add_element(2)