Use built-in Req stub for LastFm tests

test/last_fm_test.exs

@@ -1,20 +1,20 @@
 defmodule LastFmTest do
   use ExUnit.Case, async: true
 
-  alias LastFm.APIMock
-  alias LastFm.Fixtures.Artist
-  import Mox
-
-  setup :verify_on_exit!
+  alias LastFm.{Artist, Fixtures}
 
   describe "get_artist_info/1" do
     test "it returns the artist info" do
       name = "Steven Wilson"
       musicbrainz_id = Ecto.UUID.generate()
-      expected_info = Artist.get_info()
 
-      expect(APIMock, :get_artist_info, fn {:musicbrainz_id, ^musicbrainz_id}, _config ->
-        {:ok, expected_info}
+      expected_info =
+        Fixtures.Artist.get_info()
+        |> Map.get("artist")
+        |> Artist.from_api_response()
+
+      Req.Test.stub(LastFm.API, fn conn ->
+        Req.Test.json(conn, Fixtures.Artist.get_info())
       end)
 
       assert {:ok, expected_info} == LastFm.get_artist_info(musicbrainz_id, name)