Rating color advantage test WIP (lichess-org#598)

rating/src/main/scala/glicko/model.scala

@@ -34,7 +34,7 @@ val cluelessDeviation    = 230
 
 case class Player(
     glicko: Glicko,
-    numberOfResults: Int,
+    numberOfResults: Int = 0,
     lastRatingPeriodEnd: Option[Instant] = None
 ):
   export glicko.*

test-kit/src/test/scala/rating/glicko/GlickoCalculatorWithColorAdvantageTest.scala

@@ -1,4 +1,5 @@
-package chess.rating.glicko
+package chess
+package rating.glicko
 
 import cats.syntax.all.*
 import munit.ScalaCheckSuite
@@ -12,3 +13,43 @@ class RatingCalculatorWithColorAdvantageTest extends ScalaCheckSuite with chess.
   )
 
   // test that the rating calculator correctly applies the color advantage
+  import Outcome.*
+  // http://www.glicko.net/glicko/glicko2.pdf
+  // If the player is unrated, set the rating to 1500
+  // and the RD to 350. Set the player’s volatility to
+  // 0.06 (this value depends on the particular application)
+  val RD: Double = 350d
+  val V: Double = 0.06d
+
+  private def ratingDiff(r: Int, opRating: Int, outcome: Outcome, expected: Int)(using
+      munit.Location
+  ) =
+    val player = Player(Glicko(r, RD, V))
+    val opponent = Player(Glicko(opRating, RD, V))
+    val game   = Game(ByColor(player, opponent), outcome)
+    // TODO: calculator with color advantage
+    val calculator = GlickoCalculator()
+    calculator.computeGame(game)
+
+  test("new rating calculation over one game"):
+    ratingDiff(1500, 1500, white, 20)
+    ratingDiff(1500, 1500, black, -20)
+    ratingDiff(1500, 1500, draw, 0)
+    ratingDiff(1500, 1900, white, 37)
+    ratingDiff(1500, 1900, black, -3)
+    ratingDiff(1500, 1900, draw, 17)
+    ratingDiff(1500, 2900, white, 37)
+    ratingDiff(1500, 2900, black, -3)
+    ratingDiff(1500, 2900, draw, 17)
+    ratingDiff(1500, 1600, white, 26)
+    ratingDiff(1500, 1600, black, -14)
+    ratingDiff(1500, 1600, draw, 6)
+    ratingDiff(2000, 1600, white, 3)
+    ratingDiff(2000, 1600, black, -37)
+    ratingDiff(2000, 1600, draw, -17)
+    ratingDiff(2000, 1000, white, 3)
+    ratingDiff(2000, 1000, black, -37)
+    ratingDiff(2000, 1000, draw, -17)
+    ratingDiff(2000, 1900, white, 14)
+    ratingDiff(2000, 1900, black, -26)
+    ratingDiff(2000, 1900, draw, -6)