word_stats_test.exs

defmodule WordStats do
  def letter_frequency words do
    words
    |> Enum.reduce(%{}, fn(word, map) ->
      word
      |> String.graphemes
      |> Enum.reduce(map, fn(letter, map) ->
           Map.update(map, letter, 1, &(&1+1))
      end)
    end)
  end
end

defmodule TaskPlaygroundTest do
  use ExUnit.Case

  test "the truth" do
    assert 1 + 1 == 2
    #words = File.read!("/usr/share/dict/words") |> String.split("\n")
    words = [
      "cat",
      "bag"
    ]
    assert %{"c" => 1, "a" => 2, "t" => 1, "b" => 1, "g" => 1} == WordStats.letter_frequency(words)
  end
end