average_property.ex

property "index number is always it's average in all indexes" do
      check all size <- integer(1..100),
                number_lists <- list_of(number_list(size), min_length: 1, max_length: 100) do
        # since this test is based on index it also tests that ordering is maintained
        Enum.map(1..(size - 1), fn index ->
          index_avg =
            Enum.map(number_lists, fn number_list -> Enum.at(number_list, index) end)
            |> Enum.filter(fn value -> value != 0 && value != nil end)
            |> Math.Enum.mean()

          assert MissingData.average_list(number_lists) |> Enum.at(index) == index_avg
        end)
      end
end