From 71e06435bfbf0305fba00731cbbd6d875e2a08dd Mon Sep 17 00:00:00 2001
From: avitex <theavitex@gmail.com>
Date: Wed, 29 Nov 2017 13:10:02 +1100
Subject: [PATCH] Add tests and example for `win_probability`

---
 lib/glicko.ex        |  7 +++++++
 test/glicko_test.exs | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/lib/glicko.ex b/lib/glicko.ex
index c8d3c1e..b2435fc 100644
--- a/lib/glicko.ex
+++ b/lib/glicko.ex
@@ -21,6 +21,13 @@ defmodule Glicko do
 		iex> Glicko.new_rating(player, [], [system_constant: 0.5])
 		{1.5e3, 200.27141669877065}
 
+	Calculate the probability of a player winning against an opponent.
+
+		iex> player = Player.new_v1
+		iex> opponent = Player.new_v1
+		iex> Glicko.win_probability(player, opponent)
+		0.5
+
 	"""
 
 	alias __MODULE__.{
diff --git a/test/glicko_test.exs b/test/glicko_test.exs
index dc04122..2785f47 100644
--- a/test/glicko_test.exs
+++ b/test/glicko_test.exs
@@ -35,4 +35,16 @@ defmodule GlickoTest do
 
 		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