JUnitFormatter that outputs memory usage to a file

test_mem.ex

defmodule TestMem do
  @moduledoc """
  JUnitFormatter that outputs memory usage to a file.
  Useful to measure your test suite's memory consumption.
  """

  use GenServer

  @impl true
  def init(_opts) do
    file = File.open!("memory_usage.csv", [:write, {:delayed_write, 1000, 200}])
    {:ok, %{file: file}}
  end

  @impl true
  def handle_cast({:test_finished, %ExUnit.Test{state: nil}}, config) do
    IO.binwrite(config.file, "#{DateTime.utc_now()},#{:erlang.memory(:total)}\n")
    {:noreply, config}
  end

  def handle_cast({:test_finished, %ExUnit.Test{state: {:failed, _failed}}}, config) do
    IO.binwrite(config.file, "#{DateTime.utc_now()},#{:erlang.memory(:total)}\n")
    {:noreply, config}
  end

  def handle_cast(_event, config), do: {:noreply, config}
end