glicko-elixir/test/glicko_test.exs

defmodule GlickoTest do
	use ExUnit.Case

	alias Glicko.{
		Player,
		Result,
	}

	doctest Glicko

	@player [rating: 1500, rating_deviation: 200] |> Player.new_v1 |> Player.to_v2

	@results [
		Result.new(Player.new_v1([rating: 1400, rating_deviation: 30]), :win),
		Result.new(Player.new_v1([rating: 1550, rating_deviation: 100]), :loss),
		Result.new(Player.new_v1([rating: 1700, rating_deviation: 300]), :loss),
	]

	@valid_player_rating_after_results 1464.06 |> Player.scale_rating_to(:v2)
	@valid_player_rating_deviation_after_results 151.52 |> Player.scale_rating_deviation_to(:v2)
	@valid_player_volatility_after_results 0.05999

	@valid_player_rating_deviation_after_no_results 200.2714 |> Player.scale_rating_deviation_to(:v2)

	test "new rating (with results)" do
		player = Glicko.new_rating(@player, @results, [system_constant: 0.5])

		assert_in_delta Player.rating(player), @valid_player_rating_after_results, 1.0e-4
		assert_in_delta Player.rating_deviation(player), @valid_player_rating_deviation_after_results, 1.0e-4
		assert_in_delta Player.volatility(player), @valid_player_volatility_after_results, 1.0e-5
	end

	test "new rating (no results)" do
		player = Glicko.new_rating(@player, [])

		assert_in_delta Player.rating_deviation(player), @valid_player_rating_deviation_after_no_results, 1.0e-4
	end

	test "win probability with same ratings" do
		assert Glicko.win_probability(Player.new_v1, Player.new_v1) == 0.5
	end

	test "win probability with better opponent" do
		assert Glicko.win_probability(Player.new_v1([rating: 1500]), Player.new_v1([rating: 1600])) < 0.5
	end

	test "win probability with better player" do
		assert Glicko.win_probability(Player.new_v1([rating: 1600]), Player.new_v1([rating: 1500])) > 0.5
	end
end