Add note about SQLite RANDOM function

test/music_library/collection_test.exs

@@ -101,6 +101,8 @@ defmodule MusicLibrary.CollectionTest do
     setup [:fill_collection]
 
     test "returns a random record", %{collection: collection} do
+      # NOTE: we can't control randomness in the test, because the `RANDOM()` function
+      # in SQLite doesn't support a seed.
       random_record = Collection.get_latest_record!()
       collection_ids = Enum.map(collection, & &1.id)