feat: Add ability to start and stop HTTP listeners. (#1)

Reviewed-on: https://code.harton.nz/bivouac/wayfarer/pulls/1 Co-authored-by: James Harton <james@harton.nz> Co-committed-by: James Harton <james@harton.nz>
2023-10-14 14:18:48 +13:00 · 2023-10-14 14:18:48 +13:00 · 20c5ce6f44
commit 20c5ce6f44
parent cc9e8978ff
13 changed files with 405 additions and 17 deletions
--- a/config/config.exs
+++ b/config/config.exs
@ -7,3 +7,6 @@ config :git_ops,
  manage_mix_version?: true,
  version_tag_prefix: "v",
  manage_readme_version: "README.md"
+
+config :wayfarer,
+  start_listeners?: config_env() != :test
--- a/lib/wayfarer.ex
+++ b/lib/wayfarer.ex
@ -2,17 +2,4 @@ defmodule Wayfarer do
  @moduledoc """
  Documentation for `Wayfarer`.
  """
-
-  @doc """
-  Hello world.
-
-  ## Examples
-
-      iex> Wayfarer.hello()
-      :world
-
-  """
-  def hello do
-    :world
-  end
 end
--- a/lib/wayfarer/application.ex
+++ b/lib/wayfarer/application.ex
@ -7,6 +7,15 @@ defmodule Wayfarer.Application do
  @spec start(any, any) :: {:error, any} | {:ok, pid}
  def start(_type, _args) do
    []
+    |> start_listeners?()
    |> Supervisor.start_link(strategy: :one_for_one, name: Wayfarer.Supervisor)
  end
+
+  defp start_listeners?(children) do
+    if Application.get_env(:wayfarer, :start_listeners?, true) do
+      Enum.concat(children, [Wayfarer.Listener.Supervisor])
+    else
+      children
+    end
+  end
 end
--- a/lib/wayfarer/listener.ex
+++ b/lib/wayfarer/listener.ex
@ -0,0 +1,23 @@
+defmodule Wayfarer.Listener do
+  @moduledoc """
+  Manage HTTP listeners.
+  """
+
+  alias Wayfarer.Listener.DynamicSupervisor, as: ListenerSupervisor
+  alias Wayfarer.Listener.Registry, as: ListenerRegistry
+  alias Wayfarer.Listener.Server
+
+  @doc """
+  Start listener.
+  """
+  @spec start_listener(Server.options()) :: Supervisor.on_start_child()
+  def start_listener(options),
+    do: DynamicSupervisor.start_child(ListenerSupervisor, {Server, options})
+
+  @doc """
+  Stop listener
+  """
+  @spec stop_listener(:inet.socket_address(), :inet.port_number()) :: :ok
+  def stop_listener(ip, port),
+    do: GenServer.stop({:via, Registry, {ListenerRegistry, {ip, port}}}, :normal)
+end
--- a/lib/wayfarer/listener/plug.ex
+++ b/lib/wayfarer/listener/plug.ex
@ -0,0 +1,21 @@
+defmodule Wayfarer.Listener.Plug do
+  @moduledoc """
+  Plug pipeline to handle inbound HTTP connections.
+  """
+  import Plug.Conn
+  @behaviour Plug
+
+  @doc false
+  @impl true
+  def init(options) do
+    options
+  end
+
+  @doc false
+  @impl true
+  def call(conn, _opts) do
+    conn
+    |> put_resp_content_type("text/plain")
+    |> send_resp(502, "Bad Gateway")
+  end
+end
--- a/lib/wayfarer/listener/server.ex
+++ b/lib/wayfarer/listener/server.ex
@ -0,0 +1,86 @@
+defmodule Wayfarer.Listener.Server do
+  @moduledoc """
+  A GenServer which manages the state of each listener.
+  """
+
+  alias Wayfarer.Listener.Plug
+  alias Wayfarer.Listener.Registry, as: ListenerRegistry
+
+  use GenServer, restart: :transient
+  require Logger
+
+  # How long to wait for connections to drain when shutting down a listener.
+  @drain_timeout :timer.seconds(60)
+
+  @type options :: [
+          scheme: :http | :https,
+          port: :inet.port_number(),
+          ip: :inet.socket_address(),
+          keyfile: binary(),
+          certfile: binary(),
+          otp_app: binary() | atom(),
+          cipher_suite: :strong | :compatible,
+          display_plug: module(),
+          startup_log: Logger.level() | false,
+          thousand_island_options: ThousandIsland.options(),
+          http_1_options: Bandit.http_1_options(),
+          http_2_options: Bandit.http_2_options(),
+          websocket_options: Bandit.websocket_options()
+        ]
+
+  @doc false
+  @spec start_link(options) :: GenServer.on_start()
+  def start_link(options), do: GenServer.start_link(__MODULE__, options)
+
+  @doc false
+  @impl true
+  def init(options) do
+    options =
+      options
+      |> Keyword.put(:plug, Plug)
+      |> Keyword.put(:startup_log, false)
+      |> Keyword.update(
+        :thousand_island_options,
+        [shutdown_timeout: @drain_timeout],
+        &Keyword.put_new(&1, :shutdown_timeout, @drain_timeout)
+      )
+
+    with {:ok, scheme} <- fetch_required_option(options, :scheme),
+         {:ok, pid} <- Bandit.start_link(options),
+         {:ok, %{address: addr, port: port}} <- ThousandIsland.listener_info(pid),
+         {:ok, _pid} <- Registry.register(ListenerRegistry, {addr, port}, pid) do
+      listen_url = listen_url(scheme, addr, port)
+      version = Application.spec(:wayfarer)[:vsn]
+      Logger.info("Started Wayfarer v#{version} listener on #{listen_url}")
+
+      {:ok, %{server: pid, options: options, addr: addr}}
+    end
+  end
+
+  @doc false
+  @impl true
+  def terminate(:normal, %{server: server}) do
+    GenServer.stop(server, :normal)
+  end
+
+  defp fetch_required_option(options, option) do
+    case Keyword.fetch(options, option) do
+      {:ok, value} -> {:ok, value}
+      :error -> {:error, {:required_option, option}}
+    end
+  end
+
+  defp listen_url(scheme, {:local, socket_path}, _), do: "#{scheme}:#{socket_path}"
+
+  defp listen_url(scheme, address, port) when tuple_size(address) == 4 do
+    "#{scheme}://#{:inet.ntoa(address)}:#{port}"
+    |> URI.new!()
+    |> to_string()
+  end
+
+  defp listen_url(scheme, address, port) when tuple_size(address) == 8 do
+    "#{scheme}://[#{:inet.ntoa(address)}]:#{port}"
+    |> URI.new!()
+    |> to_string()
+  end
+end
--- a/lib/wayfarer/listener/supervisor.ex
+++ b/lib/wayfarer/listener/supervisor.ex
@ -0,0 +1,21 @@
+defmodule Wayfarer.Listener.Supervisor do
+  @moduledoc """
+  Supervisor for HTTP listeners.
+  """
+
+  use Supervisor
+
+  @doc false
+  @spec start_link(any) :: Supervisor.on_start()
+  def start_link(arg), do: Supervisor.start_link(__MODULE__, arg)
+
+  @doc false
+  @impl true
+  def init(_arg) do
+    [
+      {Registry, keys: :unique, name: Wayfarer.Listener.Registry},
+      {DynamicSupervisor, name: Wayfarer.Listener.DynamicSupervisor}
+    ]
+    |> Supervisor.init(strategy: :one_for_one)
+  end
+end
--- a/mix.exs
+++ b/mix.exs
@ -55,6 +55,12 @@ defmodule Wayfarer.MixProject do
    opts = [only: ~w[dev test]a, runtime: false]

    [
+      {:bandit, "~> 0.7"},
+      {:mint, "~> 1.5"},
+      {:nimble_options, "~> 1.0"},
+      {:plug, "~> 1.15"},
+      {:websock, "~> 0.5"},
+
      # Dev/test
      {:credo, "~> 1.7", opts},
      {:dialyxir, "~> 1.3", opts},
@ -63,6 +69,7 @@ defmodule Wayfarer.MixProject do
      {:ex_check, "~> 0.15", opts},
      {:ex_doc, ">= 0.0.0", opts},
      {:faker, "~> 0.17", opts},
+      {:finch, "~> 0.16", opts},
      {:git_ops, "~> 2.6", opts},
      {:mix_audit, "~> 2.1", opts}
    ]
--- a/mix.lock
+++ b/mix.lock
@ -1,5 +1,7 @@
 %{
+  "bandit": {:hex, :bandit, "0.7.7", "48456d09022607a312cf723a91992236aeaffe4af50615e6e2d2e383fb6bef10", [:mix], [{:hpax, "~> 0.1.1", [hex: :hpax, repo: "hexpm", optional: false]}, {:plug, "~> 1.14", [hex: :plug, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}, {:thousand_island, "~> 0.6.7", [hex: :thousand_island, repo: "hexpm", optional: false]}, {:websock, "~> 0.5", [hex: :websock, repo: "hexpm", optional: false]}], "hexpm", "772f0a32632c2ce41026d85e24b13a469151bb8cea1891e597fb38fde103640a"},
  "bunt": {:hex, :bunt, "0.2.1", "e2d4792f7bc0ced7583ab54922808919518d0e57ee162901a16a1b6664ef3b14", [:mix], [], "hexpm", "a330bfb4245239787b15005e66ae6845c9cd524a288f0d141c148b02603777a5"},
+  "castore": {:hex, :castore, "1.0.4", "ff4d0fb2e6411c0479b1d965a814ea6d00e51eb2f58697446e9c41a97d940b28", [:mix], [], "hexpm", "9418c1b8144e11656f0be99943db4caf04612e3eaecefb5dae9a2a87565584f8"},
  "credo": {:hex, :credo, "1.7.1", "6e26bbcc9e22eefbff7e43188e69924e78818e2fe6282487d0703652bc20fd62", [:mix], [{:bunt, "~> 0.2.1", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2.8", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "e9871c6095a4c0381c89b6aa98bc6260a8ba6addccf7f6a53da8849c748a58a2"},
  "decimal": {:hex, :decimal, "2.1.1", "5611dca5d4b2c3dd497dec8f68751f1f1a54755e8ed2a966c2633cf885973ad6", [:mix], [], "hexpm", "53cfe5f497ed0e7771ae1a475575603d77425099ba5faef9394932b35020ffcc"},
  "dialyxir": {:hex, :dialyxir, "1.4.1", "a22ed1e7bd3a3e3f197b68d806ef66acb61ee8f57b3ac85fc5d57354c5482a93", [:mix], [{:erlex, ">= 0.2.6", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "84b795d6d7796297cca5a3118444b80c7d94f7ce247d49886e7c291e1ae49801"},
@ -11,14 +13,25 @@
  "ex_doc": {:hex, :ex_doc, "0.30.6", "5f8b54854b240a2b55c9734c4b1d0dd7bdd41f71a095d42a70445c03cf05a281", [:mix], [{:earmark_parser, "~> 1.4.31", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "bd48f2ddacf4e482c727f9293d9498e0881597eae6ddc3d9562bd7923375109f"},
  "faker": {:hex, :faker, "0.17.0", "671019d0652f63aefd8723b72167ecdb284baf7d47ad3a82a15e9b8a6df5d1fa", [:mix], [], "hexpm", "a7d4ad84a93fd25c5f5303510753789fc2433ff241bf3b4144d3f6f291658a6a"},
  "file_system": {:hex, :file_system, "0.2.10", "fb082005a9cd1711c05b5248710f8826b02d7d1784e7c3451f9c1231d4fc162d", [:mix], [], "hexpm", "41195edbfb562a593726eda3b3e8b103a309b733ad25f3d642ba49696bf715dc"},
+  "finch": {:hex, :finch, "0.16.0", "40733f02c89f94a112518071c0a91fe86069560f5dbdb39f9150042f44dcfb1a", [:mix], [{:castore, "~> 0.1 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: false]}, {:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:mint, "~> 1.3", [hex: :mint, repo: "hexpm", optional: false]}, {:nimble_options, "~> 0.4 or ~> 1.0", [hex: :nimble_options, repo: "hexpm", optional: false]}, {:nimble_pool, "~> 0.2.6 or ~> 1.0", [hex: :nimble_pool, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "f660174c4d519e5fec629016054d60edd822cdfe2b7270836739ac2f97735ec5"},
  "git_cli": {:hex, :git_cli, "0.3.0", "a5422f9b95c99483385b976f5d43f7e8233283a47cda13533d7c16131cb14df5", [:mix], [], "hexpm", "78cb952f4c86a41f4d3511f1d3ecb28edb268e3a7df278de2faa1bd4672eaf9b"},
  "git_ops": {:hex, :git_ops, "2.6.0", "e0791ee1cf5db03f2c61b7ebd70e2e95cba2bb9b9793011f26609f22c0900087", [:mix], [{:git_cli, "~> 0.2", [hex: :git_cli, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.0", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "b98fca849b18aaf490f4ac7d1dd8c6c469b0cc3e6632562d366cab095e666ffe"},
+  "hpax": {:hex, :hpax, "0.1.2", "09a75600d9d8bbd064cdd741f21fc06fc1f4cf3d0fcc335e5aa19be1a7235c84", [:mix], [], "hexpm", "2c87843d5a23f5f16748ebe77969880e29809580efdaccd615cd3bed628a8c13"},
  "jason": {:hex, :jason, "1.4.1", "af1504e35f629ddcdd6addb3513c3853991f694921b1b9368b0bd32beb9f1b63", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "fbb01ecdfd565b56261302f7e1fcc27c4fb8f32d56eab74db621fc154604a7a1"},
  "makeup": {:hex, :makeup, "1.1.0", "6b67c8bc2882a6b6a445859952a602afc1a41c2e08379ca057c0f525366fc3ca", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "0a45ed501f4a8897f580eabf99a2e5234ea3e75a4373c8a52824f6e873be57a6"},
  "makeup_elixir": {:hex, :makeup_elixir, "0.16.1", "cc9e3ca312f1cfeccc572b37a09980287e243648108384b97ff2b76e505c3555", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}, {:nimble_parsec, "~> 1.2.3 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e127a341ad1b209bd80f7bd1620a15693a9908ed780c3b763bccf7d200c767c6"},
  "makeup_erlang": {:hex, :makeup_erlang, "0.1.2", "ad87296a092a46e03b7e9b0be7631ddcf64c790fa68a9ef5323b6cbb36affc72", [:mix], [{:makeup, "~> 1.0", [hex: :makeup, repo: "hexpm", optional: false]}], "hexpm", "f3f5a1ca93ce6e092d92b6d9c049bcda58a3b617a8d888f8e7231c85630e8108"},
+  "mime": {:hex, :mime, "2.0.5", "dc34c8efd439abe6ae0343edbb8556f4d63f178594894720607772a041b04b02", [:mix], [], "hexpm", "da0d64a365c45bc9935cc5c8a7fc5e49a0e0f9932a761c55d6c52b142780a05c"},
+  "mint": {:hex, :mint, "1.5.1", "8db5239e56738552d85af398798c80648db0e90f343c8469f6c6d8898944fb6f", [:mix], [{:castore, "~> 0.1.0 or ~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:hpax, "~> 0.1.1", [hex: :hpax, repo: "hexpm", optional: false]}], "hexpm", "4a63e1e76a7c3956abd2c72f370a0d0aecddc3976dea5c27eccbecfa5e7d5b1e"},
  "mix_audit": {:hex, :mix_audit, "2.1.1", "653aa6d8f291fc4b017aa82bdb79a4017903902ebba57960ef199cbbc8c008a1", [:make, :mix], [{:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: false]}, {:yaml_elixir, "~> 2.9", [hex: :yaml_elixir, repo: "hexpm", optional: false]}], "hexpm", "541990c3ab3a7bb8c4aaa2ce2732a4ae160ad6237e5dcd5ad1564f4f85354db1"},
+  "nimble_options": {:hex, :nimble_options, "1.0.2", "92098a74df0072ff37d0c12ace58574d26880e522c22801437151a159392270e", [:mix], [], "hexpm", "fd12a8db2021036ce12a309f26f564ec367373265b53e25403f0ee697380f1b8"},
  "nimble_parsec": {:hex, :nimble_parsec, "1.3.1", "2c54013ecf170e249e9291ed0a62e5832f70a476c61da16f6aac6dca0189f2af", [:mix], [], "hexpm", "2682e3c0b2eb58d90c6375fc0cc30bc7be06f365bf72608804fb9cffa5e1b167"},
+  "nimble_pool": {:hex, :nimble_pool, "1.0.0", "5eb82705d138f4dd4423f69ceb19ac667b3b492ae570c9f5c900bb3d2f50a847", [:mix], [], "hexpm", "80be3b882d2d351882256087078e1b1952a28bf98d0a287be87e4a24a710b67a"},
+  "plug": {:hex, :plug, "1.15.1", "b7efd81c1a1286f13efb3f769de343236bd8b7d23b4a9f40d3002fc39ad8f74c", [:mix], [{:mime, "~> 1.0 or ~> 2.0", [hex: :mime, repo: "hexpm", optional: false]}, {:plug_crypto, "~> 1.1.1 or ~> 1.2 or ~> 2.0", [hex: :plug_crypto, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4.3 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "459497bd94d041d98d948054ec6c0b76feacd28eec38b219ca04c0de13c79d30"},
+  "plug_crypto": {:hex, :plug_crypto, "2.0.0", "77515cc10af06645abbfb5e6ad7a3e9714f805ae118fa1a70205f80d2d70fe73", [:mix], [], "hexpm", "53695bae57cc4e54566d993eb01074e4d894b65a3766f1c43e2c61a1b0f45ea9"},
+  "telemetry": {:hex, :telemetry, "1.2.1", "68fdfe8d8f05a8428483a97d7aab2f268aaff24b49e0f599faa091f1d4e7f61c", [:rebar3], [], "hexpm", "dad9ce9d8effc621708f99eac538ef1cbe05d6a874dd741de2e689c47feafed5"},
+  "thousand_island": {:hex, :thousand_island, "0.6.7", "3a91a7e362ca407036c6691e8a4f6e01ac8e901db3598875863a149279ac8571", [:mix], [{:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "541a5cb26b88adf8d8180b6b96a90f09566b4aad7a6b3608dcac969648cf6765"},
+  "websock": {:hex, :websock, "0.5.3", "2f69a6ebe810328555b6fe5c831a851f485e303a7c8ce6c5f675abeb20ebdadc", [:mix], [], "hexpm", "6105453d7fac22c712ad66fab1d45abdf049868f253cf719b625151460b8b453"},
  "yamerl": {:hex, :yamerl, "0.10.0", "4ff81fee2f1f6a46f1700c0d880b24d193ddb74bd14ef42cb0bcf46e81ef2f8e", [:rebar3], [], "hexpm", "346adb2963f1051dc837a2364e4acf6eb7d80097c0f53cbdc3046ec8ec4b4e6e"},
  "yaml_elixir": {:hex, :yaml_elixir, "2.9.0", "9a256da867b37b8d2c1ffd5d9de373a4fda77a32a45b452f1708508ba7bbcb53", [:mix], [{:yamerl, "~> 0.10", [hex: :yamerl, repo: "hexpm", optional: false]}], "hexpm", "0cb0e7d4c56f5e99a6253ed1a670ed0e39c13fc45a6da054033928607ac08dfc"},
 }
--- a/test/support/test.cert
+++ b/test/support/test.cert
@ -0,0 +1,30 @@
+-----BEGIN CERTIFICATE-----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+MP5QDhLCMUXqnq9EG5m7bNhm/paHw/OdvhyYwE+HkyzJXJidPnf44Vts+DDGv6o=
+-----END CERTIFICATE-----
--- a/test/support/test.key
+++ b/test/support/test.key
@ -0,0 +1,52 @@
+-----BEGIN PRIVATE KEY-----
+MIIJQgIBADANBgkqhkiG9w0BAQEFAASCCSwwggkoAgEAAoICAQCloAPK7f96j+y+
+Cagio/6EXTZvYlEjj9k380x/uFdoaPV4BNzGSV6nJyr7SD5gB79mxSEfo4mJr+fH
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+HvfyQy8D6gQkufWaRINIMmNukIEFlg==
+-----END PRIVATE KEY-----
--- a/test/wayfarer/listener_test.exs
+++ b/test/wayfarer/listener_test.exs
@ -0,0 +1,139 @@
+defmodule Wayfarer.ListenerTest do
+  @moduledoc false
+  use ExUnit.Case, async: false
+  alias Wayfarer.Listener
+  import ExUnit.CaptureLog
+
+  setup do
+    start_supervised!(Wayfarer.Listener.Supervisor)
+
+    start_supervised!(
+      {Finch,
+       name: :test_client,
+       pools: %{
+         default: [
+           conn_opts: [
+             transport_opts: [
+               verify: :verify_none
+             ]
+           ]
+         ]
+       }}
+    )
+
+    :ok
+  end
+
+  describe "start_listener/1" do
+    test "it returns an error when the scheme option is missing" do
+      assert {:error, {:required_option, :scheme}} = Listener.start_listener([])
+    end
+
+    test "it returns an error when an option is incorrect" do
+      assert {:error, _} = Listener.start_listener(scheme: "Marty McFly", port: random_port())
+    end
+
+    test "it can start an HTTP listener" do
+      port = random_port()
+
+      assert {:ok, _pid} =
+               Listener.start_listener(
+                 scheme: :http,
+                 ip: {127, 0, 0, 1},
+                 port: port
+               )
+
+      assert {:ok, %{status: 502}} =
+               :get
+               |> Finch.build("http://127.0.0.1:#{port}/")
+               |> Finch.request(:test_client)
+    end
+
+    test "it can start an HTTPS listener" do
+      port = random_port()
+
+      certfile = Path.join(__DIR__, "../support/test.cert")
+      keyfile = Path.join(__DIR__, "../support/test.key")
+
+      assert {:ok, _pid} =
+               Listener.start_listener(
+                 scheme: :https,
+                 ip: {127, 0, 0, 1},
+                 port: port,
+                 certfile: certfile,
+                 keyfile: keyfile
+               )
+
+      assert {:ok, %{status: 502}} =
+               :get
+               |> Finch.build("https://127.0.0.1:#{port}/")
+               |> Finch.request(:test_client)
+    end
+
+    test "it restarts listeners when they crash" do
+      port = random_port()
+
+      assert {:ok, _pid} =
+               Listener.start_listener(
+                 scheme: :http,
+                 ip: {127, 0, 0, 1},
+                 port: port
+               )
+
+      # It's up
+      assert {:ok, %{status: 502}} =
+               :get
+               |> Finch.build("http://127.0.0.1:#{port}/")
+               |> Finch.request(:test_client)
+
+      # Crash it
+      capture_log(fn ->
+        [{_, pid}] = Registry.lookup(Listener.Registry, {{127, 0, 0, 1}, port})
+        Process.exit(pid, :kill)
+      end)
+
+      # It's up again
+      assert {:ok, %{status: 502}} =
+               :get
+               |> Finch.build("http://127.0.0.1:#{port}/")
+               |> Finch.request(:test_client)
+    end
+  end
+
+  describe "stop_listener/2" do
+    test "it can shut down a listener" do
+      port = random_port()
+
+      assert {:ok, pid} =
+               Listener.start_listener(
+                 scheme: :http,
+                 ip: {127, 0, 0, 1},
+                 port: port
+               )
+
+      assert {:ok, %{status: 502}} =
+               :get
+               |> Finch.build("http://127.0.0.1:#{port}/")
+               |> Finch.request(:test_client)
+
+      Listener.stop_listener({127, 0, 0, 1}, port)
+
+      wait_until_dead(pid)
+
+      assert {:error, _} =
+               :get
+               |> Finch.build("http://127.0.0.1:#{port}/")
+               |> Finch.request(:test_client)
+    end
+  end
+
+  defp random_port, do: :rand.uniform(0xFFFF - 1000) + 1000
+
+  defp wait_until_dead(pid) do
+    if Process.alive?(pid) do
+      wait_until_dead(pid)
+    else
+      :ok
+    end
+  end
+end
--- a/test/wayfarer_test.exs
+++ b/test/wayfarer_test.exs
@ -1,8 +1,5 @@
 defmodule WayfarerTest do
+  @moduledoc false
  use ExUnit.Case
  doctest Wayfarer
-
-  test "greets the world" do
-    assert Wayfarer.hello() == :world
-  end
 end