test message logic at the sign API level (#665)

lib/engine/alerts.ex

@@ -1,4 +1,5 @@
 defmodule Engine.Alerts do
+  @behaviour Engine.AlertsAPI
   use GenServer
   require Logger
   alias Engine.Alerts.Fetcher
@@ -22,8 +23,7 @@ defmodule Engine.Alerts do
     GenServer.start_link(__MODULE__, opts, name: name)
   end
 
-  @spec max_stop_status(ets_tables(), [Fetcher.stop_id()], [Fetcher.route_id()]) ::
-          Fetcher.stop_status()
+  @impl true
   def max_stop_status(
         tables \\ %{stops_table: @stops_table, routes_table: @routes_table},
         stop_ids,
@@ -65,7 +65,7 @@ defmodule Engine.Alerts do
     end
   end
 
-  @spec init(Keyword.t()) :: {:ok, state()}
+  @impl true
   def init(opts) do
     fetch_ms = opts[:fetch_ms] || 30_000
     fetcher = opts[:fetcher] || Engine.Alerts.ApiFetcher
@@ -93,6 +93,7 @@ defmodule Engine.Alerts do
     {:ok, state}
   end
 
+  @impl true
   def handle_info(:fetch, state) do
     schedule_fetch(self(), state.fetch_ms)
 

lib/engine/alerts_api.ex

@@ -0,0 +1,4 @@
+defmodule Engine.AlertsAPI do
+  alias Engine.Alerts.Fetcher
+  @callback max_stop_status([Fetcher.stop_id()], [Fetcher.route_id()]) :: Fetcher.stop_status()
+end

lib/engine/config.ex

@@ -2,6 +2,7 @@ defmodule Engine.Config do
   @moduledoc """
   Manages the dynamic configurable pieces of the signs such as if they are on
   """
+  @behaviour Engine.ConfigAPI
 
   use GenServer
   require Logger
@@ -28,15 +29,15 @@ defmodule Engine.Config do
     GenServer.start_link(__MODULE__, [], name: __MODULE__)
   end
 
-  @spec sign_config(:ets.tab(), String.t()) :: sign_config()
+  @impl true
   def sign_config(table_name \\ @table_signs, sign_id) do
     case :ets.lookup(table_name, sign_id) do
       [{^sign_id, config}] -> config
       _ -> :off
     end
   end
 
-  @spec headway_config(:ets.tab(), String.t(), DateTime.t()) :: Headway.t() | nil
+  @impl true
   def headway_config(table_name \\ @table_headways, headway_group, current_time) do
     time_period = Headway.current_time_period(current_time)
     Headways.get_headway(table_name, {headway_group, time_period})
@@ -54,7 +55,7 @@ defmodule Engine.Config do
     schedule_update(pid, 0)
   end
 
-  @spec init(map()) :: {:ok, state}
+  @impl true
   def init(opts) do
     state = %{
       table_name_signs: @table_signs,
@@ -84,7 +85,7 @@ defmodule Engine.Config do
     ])
   end
 
-  @spec handle_info(:update, state) :: {:noreply, state}
+  @impl true
   def handle_info(:update, state) do
     schedule_update(self())
     updater = Application.get_env(:realtime_signs, :external_config_getter)

lib/engine/config_api.ex

@@ -0,0 +1,4 @@
+defmodule Engine.ConfigAPI do
+  @callback sign_config(String.t()) :: Engine.Config.sign_config()
+  @callback headway_config(String.t(), DateTime.t()) :: Engine.Config.Headway.t() | nil
+end

lib/engine/predictions.ex

@@ -7,6 +7,7 @@ defmodule Engine.Predictions do
   Offers a `for_stop/1` public interface to get a list of Predictions.Prediction's
   for a given GTFS stop.
   """
+  @behaviour Engine.PredictionsAPI
 
   use GenServer
   require Logger
@@ -25,7 +26,7 @@ defmodule Engine.Predictions do
   end
 
   @doc "The upcoming predicted times a vehicle will be at this stop"
-  @spec for_stop(String.t(), 0 | 1) :: [Predictions.Prediction.t()]
+  @impl true
   def for_stop(predictions_table_id \\ @trip_updates_table, gtfs_stop_id, direction_id) do
     case :ets.lookup(predictions_table_id, {gtfs_stop_id, direction_id}) do
       [{_, :none}] -> []
@@ -34,6 +35,7 @@ defmodule Engine.Predictions do
     end
   end
 
+  @impl true
   def init(_) do
     schedule_update(self())
 
@@ -48,6 +50,7 @@ defmodule Engine.Predictions do
      }}
   end
 
+  @impl true
   def handle_info(:update, state) do
     schedule_update(self())
     current_time = Timex.now()

lib/engine/predictions_api.ex

@@ -0,0 +1,3 @@
+defmodule Engine.PredictionsAPI do
+  @callback for_stop(String.t(), 0 | 1) :: [Predictions.Prediction.t()]
+end

lib/signs/realtime.ex

@@ -24,6 +24,7 @@ defmodule Signs.Realtime do
     :last_departure_engine,
     :config_engine,
     :alerts_engine,
+    :current_time_fn,
     :sign_updater,
     :last_update,
     :tick_audit,
@@ -58,6 +59,7 @@ defmodule Signs.Realtime do
           last_departure_engine: module(),
           config_engine: module(),
           alerts_engine: module(),
+          current_time_fn: fun(),
           sign_updater: module(),
           last_update: DateTime.t(),
           tick_audit: non_neg_integer(),
@@ -91,6 +93,12 @@ defmodule Signs.Realtime do
       last_departure_engine: last_departure_engine,
       config_engine: config_engine,
       alerts_engine: alerts_engine,
+      current_time_fn:
+        opts[:current_time_fn] ||
+          fn ->
+            time_zone = Application.get_env(:realtime_signs, :time_zone)
+            DateTime.utc_now() |> DateTime.shift_zone!(time_zone)
+          end,
       sign_updater: sign_updater,
       last_update: nil,
       tick_audit: 60,
@@ -113,8 +121,7 @@ defmodule Signs.Realtime do
     sign_routes = SourceConfig.sign_routes(sign.source_config)
     alert_status = sign.alerts_engine.max_stop_status(sign_stop_ids, sign_routes)
     sign_config = sign.config_engine.sign_config(sign.id)
-    time_zone = Application.get_env(:realtime_signs, :time_zone)
-    {:ok, current_time} = DateTime.utc_now() |> DateTime.shift_zone(time_zone)
+    current_time = sign.current_time_fn.()
 
     predictions =
       case sign.source_config do