[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/fast_indexing/youtube_rss_test.exs

@@ -1,12 +1,10 @@
 defmodule Pinchflat.FastIndexing.YoutubeRssTest do
   use Pinchflat.DataCase
-  import Mox
+
   import Pinchflat.SourcesFixtures
 
   alias Pinchflat.FastIndexing.YoutubeRss
 
-  setup :verify_on_exit!
-
   setup do
     source = source_fixture()