`Optional` tests fail periodically

[sunny-g]

Occasionally, the tests for the Optional module will fail, though usually a subsequent re-running of the tests will pass. Why?

[Ljzn]

Hello, thank you for making this amazing lib. This problem is caused by module loading order. I fixed it with:

  def valid_xdr_type?(atom) when is_atom(atom) do
    case Code.ensure_loaded(atom) do
      {:module, _} ->
        function_exported?(atom, :length, 0) and
          (function_exported?(atom, :new, 0) or function_exported?(atom, :new, 1)) and
          function_exported?(atom, :valid?, 1) and function_exported?(atom, :encode, 1) and
          function_exported?(atom, :decode, 1)

      {:error, :nofile} ->
        false
    end
  end