* Shifting Shadows - Fixed not proper handling of gained triggered abilities during step resolution of Shifting Shadows effect (fixes #6571).

Mage.Sets/src/mage/cards/m/MairsilThePretender.java

@@ -46,10 +46,12 @@ public final class MairsilThePretender extends CardImpl {
         this.power = new MageInt(4);
         this.toughness = new MageInt(4);
 
-        // When Mairsil, the Pretender enters the battlefield, you may exile an artifact or creature card from your hand or graveyard and put a cage counter on it.
+        // When Mairsil, the Pretender enters the battlefield, you may exile an artifact or creature card from your hand
+        // or graveyard and put a cage counter on it.
         this.addAbility(new EntersBattlefieldTriggeredAbility(new MairsilThePretenderExileEffect(), true));
 
-        // Mairsil, the Pretender has all activated abilities of all cards you own in exile with cage counters on them. You may activate each of those abilities only once each turn.
+        // Mairsil, the Pretender has all activated abilities of all cards you own in exile with cage counters on them. 
+        // You may activate each of those abilities only once each turn.
         Ability ability = new SimpleStaticAbility(Zone.BATTLEFIELD, new MairsilThePretenderGainAbilitiesEffect());
         this.addAbility(ability);
     }

Mage.Sets/src/mage/cards/s/ShiftingShadow.java

@@ -71,12 +71,12 @@ public final class ShiftingShadow extends CardImpl {
 
 class ShiftingShadowEffect extends OneShotEffect {
 
-    private UUID auraId;
+    private final UUID auraId;
 
     public ShiftingShadowEffect(UUID auraId) {
         super(Outcome.PutCreatureInPlay);
         this.staticText = "destroy this creature. Reveal cards from the top of your library until you reveal a creature card. "
-                + "Put that card onto the battlefield and attach Shifting Shadow to it, then put all other cards revealed this way on the bottom of your library in a random order";
+                + "Put that card onto the battlefield and attach {this} to it, then put all other cards revealed this way on the bottom of your library in a random order";
         this.auraId = auraId;
     }
 
@@ -107,6 +107,11 @@ class ShiftingShadowEffect extends OneShotEffect {
             }
             if (aura != null) {
                 enchanted.destroy(source.getSourceId(), game, false);
+                // Because this effect has two steps, we have to call the processAction method here, so that triggered effects of the target going to graveyard go to the stack
+                // If we don't do it here, gained triggered effects to the target will be removed from the following moveCards method and the applyEffcts done there.
+                // Example: {@link org.mage.test.commander.duel.MairsilThePretenderTest#MairsilThePretenderTest Test}
+                game.getState().processAction(game);
+                
                 Cards revealed = new CardsImpl();
                 Cards otherCards = new CardsImpl();
                 for (Card card : controller.getLibrary().getCards(game)) {

Mage.Tests/CommanderDuel_Mairisil_UBR.dck

@@ -0,0 +1,90 @@
+1 [DGM:11] Aetherling
+1 [JUD:77] Anger
+1 [10E:66] Arcanis the Omnipotent
+1 [SOM:28] Argent Sphinx
+1 [CHK:52] Azami, Lady of Scrolls
+1 [AVR:47] Deadeye Navigator
+1 [DRK:44] Eater of the Dead
+1 [EXO:33] Ertai, Wizard Adept
+1 [ALA:43] Fatestitcher
+1 [SOM:64] Geth, Lord of the Vault
+1 [EVE:55] Hateflayer
+1 [DKA:139] Havengul Lich
+1 [10E:87] Horseshoe Crab
+1 [ICE:136] Infernal Denizen
+1 [M12:59] Jace's Archivist
+1 [SHM:42] Knacksaw Clique
+1 [OGW:4] Kozilek, the Great Distortion
+1 [PLC:43] Magus of the Bazaar
+1 [ICE:150] Minion of Leshrac
+1 [SOM:72] Necrotic Ooze
+1 [SHM:258] Pili-Pala
+1 [MRD:47] Quicksilver Elemental
+1 [SOK:53] Sakashima the Impostor
+1 [MIR:142] Shauku, Endbringer
+1 [M15:231] Soul of New Phyrexia
+1 [PLC:110] Torchling
+1 [EMN:109] Tree of Perdition
+1 [M20:64] Leyline of Anticipation
+1 [9ED:152] Phyrexian Arena
+1 [PCY:45] Rhystic Study
+1 [RNA:245] Blood Crypt
+1 [KTK:230] Bloodstained Mire
+1 [WWK:132] Bojuka Bog
+1 [ELD:333] Command Tower
+1 [ALA:222] Crumbling Necropolis
+1 [RAV:276] Dimir Aqueduct
+1 [CON:142] Exotic Orchard
+1 [CHK:277] Hall of the Bandit Lord
+8 [IKO:263] Island
+1 [GPT:159] Izzet Boilerworks
+1 [CHK:279] Minamo, School at Water's Edge
+3 [IKO:269] Mountain
+1 [C20:298] Path of Ancestry
+1 [KTK:239] Polluted Delta
+1 [M19:254] Reliquary Tower
+1 [ONS:322] Riptide Laboratory
+1 [ORI:251] Shivan Reef
+1 [GRN:257] Steam Vents
+1 [10E:359] Sulfurous Springs
+1 [BFZ:249] Sunken Hollow
+4 [IKO:266] Swamp
+1 [10E:362] Underground River
+1 [GRN:259] Watery Grave
+1 [ODY:118] Buried Alive
+1 [3ED:105] Demonic Tutor
+1 [USG:188] Gamble
+1 [AVR:151] Reforge the Soul
+1 [EMA:108] Toxic Deluge
+1 [MB1:1603] Mana Crypt
+1 [5ED:388] Mana Vault
+1 [HOU:165] Mirage Mirror
+1 [5ED:391] Nevinyrral's Disk
+1 [CHK:268] Sensei's Divining Top
+1 [3ED:274] Sol Ring
+1 [5DN:156] Staff of Domination
+1 [LRW:263] Thousand-Year Elixir
+1 [UDS:139] Thran Dynamo
+1 [5DN:163] Vedalken Orrery
+1 [TMP:55] Capsize
+1 [C20:146] Chaos Warp
+1 [RTR:35] Cyclonic Rift
+1 [ODY:132] Entomb
+1 [INV:57] Fact or Fiction
+1 [TMP:70] Intuition
+1 [THS:65] Swan Song
+1 [RTR:111] Vandalblast
+1 [3ED:185] Wheel of Fortune
+1 [GTC:207] Whispering Madness
+1 [USG:111] Windfall
+1 [SHM:248] Cauldron of Souls
+1 [RAV:260] Dimir Signet
+1 [9ED:297] Fellwar Stone
+1 [DOM:215] Gilded Lotus
+1 [ULG:126] Grim Monolith
+1 [GTC:231] Illusionist's Bracers
+1 [GPT:152] Izzet Signet
+1 [MRD:199] Lightning Greaves
+SB: 1 [C17:41] Mairsil, the Pretender
+LAYOUT MAIN:(1,7)(CARD_TYPE,false,50)|([SHM:258],[M15:231])([SHM:248],[RAV:260],[9ED:297],[DOM:215],[ULG:126],[GTC:231],[GPT:152],[MRD:199],[MB1:1603],[5ED:388],[HOU:165],[5ED:391],[CHK:268],[3ED:274],[5DN:156],[LRW:263],[UDS:139],[5DN:163])([DGM:11],[JUD:77],[10E:66],[SOM:28],[CHK:52],[AVR:47],[DRK:44],[EXO:33],[ALA:43],[SOM:64],[EVE:55],[DKA:139],[10E:87],[ICE:136],[M12:59],[SHM:42],[OGW:4],[PLC:43],[ICE:150],[SOM:72],[MRD:47],[SOK:53],[MIR:142],[PLC:110],[EMN:109])([M20:64],[9ED:152],[PCY:45])([TMP:55],[C20:146],[RTR:35],[ODY:132],[INV:57],[TMP:70],[THS:65])([RNA:245],[KTK:230],[WWK:132],[ELD:333],[ALA:222],[RAV:276],[CON:142],[CHK:277],[IKO:263],[IKO:263],[IKO:263],[IKO:263],[IKO:263],[IKO:263],[IKO:263],[IKO:263],[GPT:159],[CHK:279],[IKO:269],[IKO:269],[IKO:269],[C20:298],[KTK:239],[M19:254],[ONS:322],[ORI:251],[GRN:257],[10E:359],[BFZ:249],[IKO:266],[IKO:266],[IKO:266],[IKO:266],[10E:362],[GRN:259])([ODY:118],[3ED:105],[USG:188],[AVR:151],[EMA:108],[RTR:111],[3ED:185],[GTC:207],[USG:111])
+LAYOUT SIDEBOARD:(1,1)(NONE,false,50)|([C17:41])

Mage.Tests/src/test/java/org/mage/test/commander/duel/MairsilThePretenderTest.java

@@ -0,0 +1,203 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package org.mage.test.commander.duel;
+
+import java.io.FileNotFoundException;
+import mage.constants.PhaseStep;
+import mage.constants.Zone;
+import mage.game.Game;
+import mage.game.GameException;
+import org.junit.Test;
+import static org.mage.test.player.TestPlayer.NO_TARGET;
+import org.mage.test.serverside.base.CardTestCommanderDuelBase;
+
+/**
+ *
+ * @author LevelX2
+ */
+public class MairsilThePretenderTest extends CardTestCommanderDuelBase {
+
+    @Override
+    protected Game createNewGameAndPlayers() throws GameException, FileNotFoundException {
+        // When Mairsil, the Pretender enters the battlefield, you may exile an artifact or creature card from your hand
+        // or graveyard and put a cage counter on it.
+        // Mairsil, the Pretender has all activated abilities of all cards you own in exile with cage counters on them. 
+        // You may activate each of those abilities only once each turn.               
+        setDecknamePlayerA("CommanderDuel_Mairisil_UBR.dck"); // Commander = Mairsil, the Pretender {1}{U}{B}{R}
+        return super.createNewGameAndPlayers();
+    }
+
+    /**
+     * Basic Test
+     */
+    @Test
+    public void useShifitingShadowTest() {
+        addCard(Zone.BATTLEFIELD, playerA, "Mountain", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Swamp", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Island", 2);
+
+        // Enchant creature
+        // Enchanted creature has haste and “At the beginning of your upkeep, destroy this creature. 
+        // Reveal cards from the top of your library until you reveal a creature card.
+        // Put that card onto the battlefield and attach Shifting Shadow to it, 
+        // then put all other cards revealed this way on the bottom of your library in a random order.”
+        addCard(Zone.HAND, playerA, "Shifting Shadow", 1); // {2}{R}
+        
+        // Tap: Draw three cards.
+        // {2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.        
+        addCard(Zone.HAND, playerA, "Arcanis the Omnipotent", 1); // Creature {3}{U}{U}{U}
+
+        setChoice(playerA, "Yes");
+        
+        castSpell(1, PhaseStep.PRECOMBAT_MAIN, playerA, "Mairsil, the Pretender");        
+        setChoice(playerA, "Yes"); // Exile a card
+        setChoice(playerA, "Arcanis the Omnipotent");
+        
+        
+        castSpell(3, PhaseStep.PRECOMBAT_MAIN, playerA, "Shifting Shadow", "Mairsil, the Pretender");
+
+        setChoice(playerA, "Yes"); // Move commander to command zone
+        setStopAt(5, PhaseStep.PRECOMBAT_MAIN);
+
+        setStrictChooseMode(true);
+        execute();
+        assertAllCommandsUsed();
+        
+        assertLife(playerA, 40);
+        assertLife(playerB, 40);
+
+        assertExileCount("Arcanis the Omnipotent", 1);
+
+        assertCommandZoneCount(playerA, "Mairsil, the Pretender", 1);
+        
+        assertPermanentCount(playerA, "Shifting Shadow", 1);        
+    }
+    /**
+     * I tried playing it in Mairsil the Pretender commander deck and found 2
+     * cases where the creature is not properly destroyed:
+     *
+     * Using Arcanis the Omnipotent ability to return my commander to hand while
+     * trigger is on the stack I got Mairsil to hand then got asked whether I
+     * want to put him in gy so I answered yes assuming it cannot be destroyed
+     * while in my hand. He got put in graveyard straight from my hand.
+     * According to Oracle rules I should get a creature from top of the deck
+     * and still have my commander in hand. After giving my commander undying
+     * with shifting shadow trigger on the stack he got put in gy with undying
+     * not triggering.
+     *
+     * All this points to the card being hardcoded to put the creature into
+     * graveyard instead of simply destroying it
+     */
+    @Test
+    public void useShifitingShadowAndArcanisTest() {
+        addCard(Zone.BATTLEFIELD, playerA, "Mountain", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Swamp", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Island", 2);
+        addCard(Zone.LIBRARY, playerA, "Silvercoat Lion", 3);
+        skipInitShuffling();
+        // Enchant creature
+        // Enchanted creature has haste and “At the beginning of your upkeep, destroy this creature. 
+        // Reveal cards from the top of your library until you reveal a creature card.
+        // Put that card onto the battlefield and attach Shifting Shadow to it, 
+        // then put all other cards revealed this way on the bottom of your library in a random order.”
+        addCard(Zone.HAND, playerA, "Shifting Shadow", 1); // {2}{R}
+        
+        // Tap: Draw three cards.
+        // {2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.        
+        addCard(Zone.HAND, playerA, "Arcanis the Omnipotent", 1); // Creature {3}{U}{U}{U}
+
+        setChoice(playerA, "Yes");
+        
+        castSpell(1, PhaseStep.PRECOMBAT_MAIN, playerA, "Mairsil, the Pretender");        
+        setChoice(playerA, "Yes"); // Exile a card
+        setChoice(playerA, "Arcanis the Omnipotent");
+        
+        
+        castSpell(3, PhaseStep.PRECOMBAT_MAIN, playerA, "Shifting Shadow", "Mairsil, the Pretender");
+
+        activateAbility(5, PhaseStep.UPKEEP, playerA, "{2}{U}{U}: Return", NO_TARGET, "At the beginning of your upkeep");
+        setChoice(playerA, "No"); // Don't move commander to command zone because it goes to hand
+
+        setStopAt(5, PhaseStep.PRECOMBAT_MAIN);
+
+        setStrictChooseMode(true);
+        execute();
+        assertAllCommandsUsed();
+        
+        assertLife(playerA, 40);
+        assertLife(playerB, 40);
+
+        assertExileCount("Arcanis the Omnipotent", 1);
+
+        assertCommandZoneCount(playerA, "Mairsil, the Pretender", 0);
+        assertHandCount(playerA, "Mairsil, the Pretender", 1);
+       
+        
+        assertGraveyardCount(playerA, "Shifting Shadow", 1);  // Goes to graveyard because commander left battlefield to hand from Arcanis ability     
+        assertPermanentCount(playerA, "Silvercoat Lion", 1); 
+    }
+    
+    @Test
+    public void useShifitingShadowAndEndlingTest() {
+        addCard(Zone.BATTLEFIELD, playerA, "Mountain", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Swamp", 1);
+        addCard(Zone.BATTLEFIELD, playerA, "Island", 2);
+        addCard(Zone.LIBRARY, playerA, "Silvercoat Lion", 3);
+        skipInitShuffling();
+        // Enchant creature
+        // Enchanted creature has haste and “At the beginning of your upkeep, destroy this creature. 
+        // Reveal cards from the top of your library until you reveal a creature card.
+        // Put that card onto the battlefield and attach Shifting Shadow to it, 
+        // then put all other cards revealed this way on the bottom of your library in a random order.”
+        addCard(Zone.HAND, playerA, "Shifting Shadow", 1); // {2}{R}
+        // Tap: Draw three cards.
+        // {2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.        
+        addCard(Zone.HAND, playerA, "Arcanis the Omnipotent", 1); // Creature {3}{U}{U}{U}        
+        // {B}: Endling gains menace until end of turn.
+        // {B}: Endling gains deathtouch until end of turn.
+        // {B}: Endling gains undying until end of turn.
+        // {1}: Endling gets +1/-1 or -1/+1 until end of turn.   
+        addCard(Zone.HAND, playerA, "Endling", 1); // Creature {3}{U}{U}{U}
+
+        
+        
+        castSpell(1, PhaseStep.PRECOMBAT_MAIN, playerA, "Mairsil, the Pretender");                
+        setChoice(playerA, "Yes"); // Exile a card
+        setChoice(playerA, "Yes"); // Exile from Hand
+        setChoice(playerA, "Endling");
+        
+        
+        castSpell(3, PhaseStep.PRECOMBAT_MAIN, playerA, "Shifting Shadow", "Mairsil, the Pretender");
+
+        activateAbility(5, PhaseStep.UPKEEP, playerA, "{B}: {this} gains Undying", NO_TARGET, "At the beginning of your upkeep");
+        setChoice(playerA, "No"); // Don't move commander to command zone because can come back by Undying
+        
+        setChoice(playerA, "Yes"); // Exile a card (Mairsil comes back from Undying)
+        setChoice(playerA, "Yes"); // Exile from hand
+        setChoice(playerA, "Arcanis the Omnipotent");
+        
+        setStopAt(5, PhaseStep.PRECOMBAT_MAIN);
+
+        setStrictChooseMode(true);
+        execute();
+        assertAllCommandsUsed();
+        
+        assertLife(playerA, 40);
+        assertLife(playerB, 40);
+
+        assertExileCount("Endling", 1);
+        assertExileCount("Arcanis the Omnipotent", 1);
+
+        assertCommandZoneCount(playerA, "Mairsil, the Pretender", 0);
+        assertGraveyardCount(playerA, "Mairsil, the Pretender", 0);
+        assertPermanentCount(playerA, "Mairsil, the Pretender", 1); // Returns from Undying
+        assertPowerToughness(playerA, "Mairsil, the Pretender", 5, 5);
+        
+        assertPermanentCount(playerA, "Shifting Shadow", 1);  // Enchants Silvercoat Lion    
+        assertPermanentCount(playerA, "Silvercoat Lion", 1); 
+    }
+
+}

Mage.Tests/src/test/java/org/mage/test/serverside/base/impl/CardTestPlayerAPIImpl.java

@@ -1600,6 +1600,15 @@ public abstract class CardTestPlayerAPIImpl extends MageTestPlayerBase implement
         player.addAction(turnNum, step, ACTIVATE_ABILITY + ability + "$target=" + String.join("^", targetNames));
     }
 
+    /**
+     * 
+     * @param turnNum
+     * @param step
+     * @param player
+     * @param ability
+     * @param targetName  use NO_TARGET if there is no target to set
+     * @param spellOnStack 
+     */
     public void activateAbility(int turnNum, PhaseStep step, TestPlayer player, String ability, String targetName, String spellOnStack) {
         // TODO: it's uses computerPlayer to execute, only ability target will work, but choices and targets commands aren't
         this.activateAbility(turnNum, step, player, ability, targetName, spellOnStack, StackClause.WHILE_ON_STACK);

Mage/src/main/java/mage/abilities/effects/common/continuous/CommanderReplacementEffect.java

@@ -91,9 +91,9 @@ public class CommanderReplacementEffect extends ReplacementEffectImpl {
     public boolean applies(GameEvent event, Ability source, Game game) {
         ZoneChangeEvent zEvent = (ZoneChangeEvent) event;
 
-        if (!game.isSimulation() && commanderId.equals(zEvent.getTargetId())) {
+//        if (!game.isSimulation() && commanderId.equals(zEvent.getTargetId())) {
-            //System.out.println("applies " + game.getTurnNum() + ": " + game.getObject(event.getTargetId()).getName() + ": " + zEvent.getFromZone() + " -> " + zEvent.getToZone() + "; " + game.getObject(zEvent.getSourceId()));
+//            System.out.println("applies " + game.getTurnNum() + ": " + game.getObject(event.getTargetId()).getName() + ": " + zEvent.getFromZone() + " -> " + zEvent.getToZone() + "; " + game.getObject(zEvent.getSourceId()));
-        }
+//        }
 
         if (zEvent.getToZone().equals(Zone.HAND) && !alsoHand) {
             return false;