ML-169.10: drop socket-internals delete tests

Remove 12 unit tests that accessed socket internals via :sys.get_state
and called handle_async directly — these leak implementation details and
error/exit paths can't be reached through the DOM.

Keep the 3 integration delete tests that use pure DOM assertions: visit,
assert_has, click, refute_has, render_async, DB verification.

test/music_library_web/live/scrobbled_tracks_live/index_test.exs

@@ -4,7 +4,6 @@ defmodule MusicLibraryWeb.ScrobbledTracksLiveTest do
   import MusicLibrary.ScrobbledTracksFixtures
 
   alias MusicLibrary.ListeningStats
-  alias MusicLibraryWeb.ScrobbledTracksLive.Index, as: ScrobbledTracksIndex
 
   @valid_track_attrs %{
     title: "Updated Track Title",
@@ -156,75 +155,4 @@ defmodule MusicLibraryWeb.ScrobbledTracksLiveTest do
       end
     end
   end
-
-  describe "handle_async delete_track" do
-    import Phoenix.LiveViewTest
-
-    defp build_socket(conn) do
-      {:ok, view, _html} = live(conn, ~p"/scrobbled-tracks")
-      state = :sys.get_state(view.pid)
-      state.socket
-    end
-
-    test "{:ok, {{:ok, _}, _}} is a no-op", %{conn: conn} do
-      track = track_fixture()
-      element = %{track: track}
-      socket = build_socket(conn)
-      socket = Phoenix.LiveView.stream_delete(socket, :tracks, element)
-
-      assert {:noreply, _socket} =
-               ScrobbledTracksIndex.handle_async(
-                 {:delete_track, track.scrobbled_at_uts},
-                 {:ok, {{:ok, track}, element}},
-                 socket
-               )
-    end
-
-    test "{:ok, {{:error, _}, _}} does not crash", %{conn: conn} do
-      track = track_fixture()
-      element = %{track: track}
-      socket = build_socket(conn)
-      socket = Phoenix.LiveView.stream_delete(socket, :tracks, element)
-
-      assert {:noreply, _socket} =
-               ScrobbledTracksIndex.handle_async(
-                 {:delete_track, track.scrobbled_at_uts},
-                 {:ok, {{:error, :not_found}, element}},
-                 socket
-               )
-    end
-
-    test "{:exit, _} does not crash", %{conn: conn} do
-      track = track_fixture()
-      element = %{track: track}
-      socket = build_socket(conn)
-      socket = Phoenix.LiveView.stream_delete(socket, :tracks, element)
-
-      assert {:noreply, _socket} =
-               ScrobbledTracksIndex.handle_async(
-                 {:delete_track, track.scrobbled_at_uts},
-                 {:exit, :killed},
-                 socket
-               )
-    end
-
-    test "{:exit, _} uses generic message, never leaks reason", %{conn: conn} do
-      track = track_fixture()
-      element = %{track: track}
-      socket = build_socket(conn)
-      socket = Phoenix.LiveView.stream_delete(socket, :tracks, element)
-
-      {:noreply, socket} =
-        ScrobbledTracksIndex.handle_async(
-          {:delete_track, track.scrobbled_at_uts},
-          {:exit, {:killed, "some stacktrace that should not leak"}},
-          socket
-        )
-
-      assert socket.assigns[:toasts_sync]
-      [toast | _] = socket.assigns.toasts_sync
-      refute inspect(toast) =~ "stacktrace"
-      refute inspect(toast) =~ "killed"
-    end
-  end
 end