[Housekeeping] Improve test stability (#232)

* Ensured all tests use at least the DataCase module

* addressed one flakey test

* More flakey tests

* Consolidated Mox usage

test/pinchflat/yt_dlp/media_collection_test.exs

@@ -1,6 +1,6 @@
 defmodule Pinchflat.YtDlp.MediaCollectionTest do
   use Pinchflat.DataCase
-  import Mox
+
   import Pinchflat.SourcesFixtures
 
   alias Pinchflat.YtDlp.Media
@@ -8,8 +8,6 @@ defmodule Pinchflat.YtDlp.MediaCollectionTest do
 
   @channel_url "https://www.youtube.com/c/PinchflatTestChannel"
 
-  setup :verify_on_exit!
-
   describe "get_media_attributes_for_collection/2" do
     test "returns a list of video attributes with no blank elements" do
       expect(YtDlpRunnerMock, :run, fn _url, _opts, _ot, _addl_opts ->