I have an umbrella app.

Some of the apps inside depend on other apps in the umbrella, unsurprisingly.

I’m writing a test for one of the apps which currently relies on starting a process using one of the other apps.

Almost all such processes across these apps use an app-specific or purpose-specific Registry.

This is the error I get:

23:04:13.529 [error] GenServer {Registry.Mobs, 1} terminating
** (stop) exited in: GenServer.call({:via, Registry, {World.LocationRegistry, "2"}}, {:mobs, #Function<1.42779424/1 in Mobs.Bird.handle_cast/2>}, 5000)
    ** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
    (elixir) lib/gen_server.ex:729: GenServer.call/3
    (mobs) lib/mobs/bird.ex:79: Mobs.Bird.handle_cast/2
    (stdlib) gen_server.erl:601: :gen_server.try_dispatch/4
    (stdlib) gen_server.erl:667: :gen_server.handle_msg/5
    (stdlib) proc_lib.erl:247: :proc_lib.init_p_do_apply/3
Last message: {:"$gen_cast", :try_to_mate}
State: %Mobs.Bird{controller: #PID<0.395.0>, gender: :female, id: 1, lifespan: 39, location_id: "2", name: "a bird", pregnant: nil}

My test_helper.exs is trying to provide support to the mix.exs file which requires the apps by doing this:

Application.ensure_all_started(:world)
Application.ensure_all_started(:mobs)
Application.ensure_all_started(:controllers)
Application.ensure_all_started(:life)
ExUnit.start()

The World.Application module looks like this:

defmodule World.Application do
  # See http://elixir-lang.org/docs/stable/elixir/Application.html
  # for more information on OTP Applications
  @moduledoc false

  use Application

  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    # Define workers and child supervisors to be supervised
    children = [
      supervisor(Registry, [:unique, World.LocationRegistry], id: :location_registry),
      supervisor(Registry, [:unique, World.PathwayRegistry], id: :pathway_registry),
      supervisor(World, [%{spawn_locations: Application.get_env(:world, :spawn_locations)}])
    ]

    # See http://elixir-lang.org/docs/stable/elixir/Supervisor.html
    # for other strategies and supported options
    opts = [strategy: :one_for_one, name: World.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

This is the test as it stands:

defmodule Mobs.BirdTest do
  use ExUnit.Case
  doctest Mobs.Bird

  test "only mates with birds" do
    import IEx
    {:ok, foo} = World.Location.start_link(
      %World.Location{
        id: "2",
        name: "center of the universe",
        description: "what's on the tin",
        pathways: []}
    )
    female_bird = Mobs.Spawn.birth(
      %{module: Mobs.Bird, location_id: "2", gender: :female})
    male_dwarf = Mobs.Spawn.birth(
      %{module: Mobs.Dwarf, location_id: "2", gender: :male})
    :ok = Mobs.Bird.try_to_mate(female_bird)
  end
end

The obviously relevant code from Mobs.Bird is :

defmodule Mobs.Bird do
  def try_to_mate(id) do
    GenServer.cast(via_mob(id), :try_to_mate)
  end

  def handle_cast(:try_to_mate, state) do
    looking_for = case state.gender do
                    :male -> :female
                    :female -> :male
                  end

    possible_partners =
      World.Location.mobs(
              state.location_id,
              fn({{module, id}, info}) -> module == __MODULE__ && info.gender == looking_for end)

    if Enum.any? possible_partners do
      partner = Enum.random possible_partners

      case [state.gender, elem(partner, 1).gender] do
        [:male, :female] -> __MODULE__.pregnantize(elem(partner, 0))
        [:female, :male] ->  __MODULE__.pregnantize(state.id)
      end
    end
    {:noreply, state}
  end
end 

Similarly, the obviously relevant code from World.Location is :

defmodule World.Location do
  def mobs(loc_id)do
    mobs(loc_id, fn(_x) -> true end)
  end

  def mobs(loc_id, filter) do
    GenServer.call(via_tuple(loc_id), {:mobs, filter})
  end

  def handle_call({:mobs, filter}, _from, state) do
    mobs = Enum.filter(state.entities, filter)
    {:reply, mobs, state}
  end
end