add tests

test/support/external_format_handler.ex

@@ -2,6 +2,22 @@ defmodule FeedReader.TestSupport.ExternalFormatHandler do
   @moduledoc false
   @behaviour Saxy.Handler
 
+  alias FeedReader.Feed
+
   @impl true
+  def handle_event(:start_document, _data, %{opts: opts} = state) do
+    if Keyword.get(opts, :emit_event), do: emit_event(state)
+
+    {:ok, state}
+  end
+
+  def handle_event(:end_document, _data, %{opts: opts} = state) do
+    if Keyword.get(opts, :emit_event), do: emit_event(state)
+
+    {:ok, state}
+  end
+
   def handle_event(_event_type, _data, state), do: {:ok, state}
+
+  defp emit_event(state), do: state.event_sink.({:feed, %Feed{title: "External", type: :rss}})
 end