error

  1) test sorts by the number of fields present in the doc (FindGoodSolrDocTest)
     test/find_good_solr_doc_test.exs:24
     ** (FunctionClauseError) no function clause matching in Enumerable.Function.reduce/3
     stacktrace:
       (elixir) lib/enum.ex:2198: Enumerable.Function.reduce(#Function<0.18085451/1 in FindGoodSolrDocTest.test sorts by the number of fields present in the doc/1>, {:cont, []}, #Function<32.13715154/2 in Enum.reduce/3>)
       (elixir) lib/enum.ex:1256: Enum.reduce/3
       (elixir) lib/enum.ex:1545: Enum.sort/2
       test/find_good_solr_doc_test.exs:27

fails.ex

  test "sorts by the number of fields present in the doc" do
    output = @docs
             |> Enum.map &({&1["id"], (Map.keys(&1) |> Enum.count)})
             |> Enum.sort(fn({_, a}, {_, b}) -> a > b end)

    IO.inspect output
  end

works.ex

  test "sorts by the number of fields present in the doc" do
    list = @docs
           |> Enum.map &({&1["id"], (Map.keys(&1) |> Enum.count)})

    output = Enum.sort(list, fn({_, a}, {_, b}) -> a > b end)

    IO.inspect output
  end