Add large battery of tests, primarily workers

test/music_library/artist_chat_test.exs

@@ -0,0 +1,10 @@
+defmodule MusicLibrary.ArtistChatTest do
+  use ExUnit.Case
+
+  alias MusicLibrary.ArtistChat
+
+  test "implements the Chat behaviour" do
+    Code.ensure_loaded!(ArtistChat)
+    assert function_exported?(ArtistChat, :stream_response, 3)
+  end
+end