gen_server_test.exs

defmodule GenServerTestTest do
  use ExUnit.Case
  doctest GenServerTest

  setup do
IO.puts "setup starting"
    { :ok, pid } = GenServerTest.start_link()
IO.puts "setup started"

    on_exit fn ->
IO.puts "on_exit, stopping"
      GenServerTest.stop()
IO.puts "on_exit, stopped"
    end

    { :ok, [pid: pid] }
  end

  test "the truth" do
IO.puts "test starting"
    assert 1 + 1 == 2
IO.puts "test stopping"
  end
end

my_gen_server.ex

defmodule GenServerTest do
  use GenServer

  def start_link() do
IO.puts "gen_server start_link"
    result = GenServer.start_link(__MODULE__, [], [])
IO.puts "gen_server started"
    result
  end

  def stop() do
IO.puts "gen_server stop"
    result = GenServer.stop(__MODULE__)
IO.puts "gen_server stopped"
    result
  end
end

output.txt

/tmp/gen_server_test$ mix test
setup starting
gen_server start_link
gen_server started
setup started
test starting
test stopping
on_exit, stopping
gen_server stop


  1) test the truth (GenServerTestTest)
     test/gen_server_test_test.exs:19
     ** (exit) no process
     stacktrace:
       (stdlib) gen.erl:260: :gen.do_for_proc/2
       (gen_server_test) lib/gen_server_test.ex:13: GenServerTest.stop/0
       test/gen_server_test_test.exs:12: anonymous fn/0 in GenServerTestTest.__ex_unit_setup_0/1
       (ex_unit) lib/ex_unit/on_exit_handler.ex:82: ExUnit.OnExitHandler.exec_callback/1
       (ex_unit) lib/ex_unit/on_exit_handler.ex:66: ExUnit.OnExitHandler.on_exit_runner_loop/0



Finished in 0.05 seconds (0.05s on load, 0.00s on tests)
1 test, 1 failure

Randomized with seed 601203