cassidoo string deletion test

limited_imaginations.ex

defmodule LimitedImaginations do
  @spec check_for_deletion(
          String.grapheme(),
          {:ok, number(), String.t()}
        ) :: {:ok, number(), String.t()}

  @spec every_other(String.t()) :: {:ok, number(), String.t()}
  def check_for_deletion(el, {:ok, 0, ""}) do
    {:ok, 0, el}
  end

  def check_for_deletion(el, {:ok, count, builder}) do
    if String.last(builder) == el do
      {:ok, count + 1, builder}
    else
      {:ok, count, builder <> el}
    end
  end

  def every_other(input) do
    String.graphemes(input)
    |> Enum.reduce(
      {:ok, 0, ""},
      &check_for_deletion/2
    )
  end
end

limited_imaginations_test.ex

defmodule LimitedImaginationsTest do
  use ExUnit.Case
  doctest LimitedImaginations

  test "has no matching ajacent characters 1" do
    assert LimitedImaginations.every_other("xxyxxy") == {:ok, 2, "xyxy"}
  end

  test "has no matching ajacent characters 2" do
    assert LimitedImaginations.every_other("yyyyy") == {:ok, 4, "y"}
  end
end