performance: added day/night performance test for transform ability (disabled by default, see DayNightTest, related to #11285), added day/night rules ref

Mage/src/main/java/mage/abilities/keyword/DayboundAbility.java

@@ -51,6 +51,8 @@ class DayboundEffect extends ContinuousEffectImpl {
     @Override
     public boolean apply(Game game, Ability source) {
         if (!game.hasDayNight()) {
+            // 702.145d
+            // Any time a player controls a permanent with daybound, if it’s neither day nor night, it becomes day.
             game.setDaytime(true);
         }
         return true;

Mage/src/main/java/mage/abilities/keyword/NightboundAbility.java

@@ -57,6 +57,9 @@ class NightboundEffect extends ContinuousEffectImpl {
     @Override
     public boolean apply(Game game, Ability source) {
         if (!game.hasDayNight()) {
+            // 702.145f
+            // Any time a player controls a permanent that is back face up with nightbound and it’s day,
+            // that player transforms that permanent. This happens immediately and isn’t a state-based action.
             game.setDaytime(false);
         }
         return true;

Mage/src/main/java/mage/game/turn/UntapStep.java

@@ -29,7 +29,15 @@ public class UntapStep extends Step {
     @Override
     public void beginStep(Game game, UUID activePlayerId) {
         super.beginStep(game, activePlayerId);
+
+        // 726.2.
+        // As the second part of the untap step, the game checks the previous turn to see
+        // if the game’s day/night designation should change. See rule 502, “Untap Step.”
+        //
+        // Before a player untaps their permanents during the untap step, the game checks to see
+        // if the day/night designation should change. (2021-09-24)
         handleDayNight(game);
+
         Player activePlayer = game.getPlayer(activePlayerId);
         //20091005 - 502.1/703.4a
         activePlayer.phasing(game);
@@ -52,8 +60,18 @@ public class UntapStep extends Step {
                 .getWatcher(CastSpellLastTurnWatcher.class)
                 .getActivePlayerPrevTurnCount();
         if (game.checkDayNight(true) && previousSpells == 0) {
+            // 726.2a
+            // If it’s day and the previous turn’s active player didn’t cast any spells during that turn,
+            // it becomes night. Multiplayer games using the shared team turns option (see rule 805)
+            // use a modified rule: if it’s day and no player from the previous turn’s active team cast a
+            // spell during that turn, it becomes night.
             game.setDaytime(false);
         } else if (game.checkDayNight(false) && previousSpells >= 2) {
+            // 726.2b
+            // If it’s night, and previous turn’s active player cast two or more spells during the previous turn,
+            // it becomes day. Multiplayer games using the shared team turns option (see rule 805) use a modified
+            // rule: if it’s night and any player from the previous turn’s active team cast two or more spells
+            // during that turn, it becomes day.
             game.setDaytime(true);
         }
     }