Refactor test runtime ownership

mix.exs

@@ -6,6 +6,7 @@ defmodule Parrhesia.MixProject do
       app: :parrhesia,
       version: "0.5.0",
       elixir: "~> 1.18",
+      elixirc_paths: elixirc_paths(Mix.env()),
       start_permanent: Mix.env() == :prod,
       deps: deps(),
       aliases: aliases()
@@ -20,6 +21,9 @@ defmodule Parrhesia.MixProject do
     ]
   end
 
+  defp elixirc_paths(:test), do: ["lib", "test/support"]
+  defp elixirc_paths(_env), do: ["lib"]
+
   def cli do
     [preferred_envs: [precommit: :test, bench: :test]]
   end