   If you want to run tests manually, you can set the `:autorun` option
   to `false` and use `run/0` to run tests.
   """
+  @spec start(Keyword.t()) :: nil | list(fun)
   def start(options \\ []) do
     {:ok, _} = Application.ensure_all_started(:ex_unit)
 

  @doc """
  Returns ExUnit configuration.
  """
  def configuration do
    Application.get_all_env(:ex_unit)
    |> put_seed()

  reverse order. In other words, the last callback set will be the first to be
  called.
  """
  @spec after_suite((suite_result() -> any)) :: :ok
  def after_suite(function) when is_function(function) do
    current_callbacks = Application.fetch_env!(:ex_unit, :after_suite)
    configure(after_suite: [function | current_callbacks])
