How to unit-test a small Elixir library inline, without any project management cruft (at least in the early stages)

sparkline.exs

defmodule Sparkline do
  def draw(str) do
    values = str |> String.split(~r/[, ]+/)
                 |> Enum.map(&(elem(Float.parse(&1), 0)))
    {min, max} = {Enum.min(values), Enum.max(values)}
    Enum.map(values, &(round((&1 - min) / (max - min) * 7 + 0x2581)))
  end
end

# run this inline suite with "elixir #{__ENV__.file} test"
if System.argv |> List.first == "test" do
  ExUnit.start
  defmodule SparklineTest do
    use ExUnit.Case, async: true
    test "sparkline" do
      assert Sparkline.draw("1 2.5 3 5, 3 1") == '▁▄▅█▅▁'
    end
  end
end