fix #11520 (Elite Spellbinder)

and similar card InvasionOfGobakhan

Mage.Sets/src/mage/cards/e/EliteSpellbinder.java

@@ -4,6 +4,7 @@ import java.util.UUID;
 import mage.MageInt;
 import mage.MageObjectReference;
 import mage.abilities.Ability;
+import mage.abilities.SpellAbility;
 import mage.abilities.common.EntersBattlefieldTriggeredAbility;
 import mage.abilities.effects.AsThoughEffectImpl;
 import mage.abilities.effects.OneShotEffect;
@@ -151,6 +152,9 @@ class EliteSpellbinderCostEffect extends CostModificationEffectImpl {
 
     @Override
     public boolean applies(Ability abilityToModify, Ability source, Game game) {
+        if (!(abilityToModify instanceof SpellAbility)) {
+            return false;
+        }
         if (game.inCheckPlayableState()) { // during playable check, the card is still in exile zone, the zcc is one less
             UUID cardtoCheckId = CardUtil.getMainCardId(game, abilityToModify.getSourceId());
             return mor.getSourceId().equals(cardtoCheckId)

Mage.Sets/src/mage/cards/i/InvasionOfGobakhan.java

@@ -2,6 +2,7 @@ package mage.cards.i;
 
 import mage.MageObjectReference;
 import mage.abilities.Ability;
+import mage.abilities.SpellAbility;
 import mage.abilities.common.EntersBattlefieldTriggeredAbility;
 import mage.abilities.common.SiegeAbility;
 import mage.abilities.effects.AsThoughEffectImpl;
@@ -151,6 +152,9 @@ class InvasionOfGobakhanCostEffect extends CostModificationEffectImpl {
 
     @Override
     public boolean applies(Ability abilityToModify, Ability source, Game game) {
+        if (!(abilityToModify instanceof SpellAbility)) {
+            return false;
+        }
         if (game.inCheckPlayableState()) { // during playable check, the card is still in exile zone, the zcc is one less
             UUID cardtoCheckId = CardUtil.getMainCardId(game, abilityToModify.getSourceId());
             return mor.getSourceId().equals(cardtoCheckId)

Mage.Tests/src/test/java/org/mage/test/cards/single/stx/EliteSpellbinderTest.java

@@ -0,0 +1,49 @@
+package org.mage.test.cards.single.stx;
+
+import mage.constants.PhaseStep;
+import mage.constants.Zone;
+import org.junit.Test;
+import org.mage.test.serverside.base.CardTestPlayerBase;
+
+/**
+ * @author xenohedron
+ */
+public class EliteSpellbinderTest extends CardTestPlayerBase {
+
+    // reported bug #11520
+    private static final String spellbinder = "Elite Spellbinder";
+    // When Elite Spellbinder enters the battlefield, look at target opponent’s hand.
+    // You may exile a nonland card from it. For as long as that card remains exiled, its owner may play it.
+    // A spell cast this way costs {2} more to cast.
+
+    private static final String cascader = "Maelstrom Colossus"; // 8 mana creature with cascade
+    private static final String bolt = "Lightning Bolt";
+
+    @Test
+    public void testCostIncreaseDoesntAffectCascade() {
+        addCard(Zone.BATTLEFIELD, playerA, "Plains", 3);
+        addCard(Zone.HAND, playerA, spellbinder);
+        addCard(Zone.BATTLEFIELD, playerB, "Wastes", 10);
+        addCard(Zone.HAND, playerB, cascader);
+        addCard(Zone.LIBRARY, playerB, bolt); // to be cascaded into
+        addCard(Zone.LIBRARY, playerB, "Shock"); // top of library, gets drawn
+        skipInitShuffling();
+
+        castSpell(1, PhaseStep.PRECOMBAT_MAIN, playerA, spellbinder);
+        addTarget(playerA, playerB); // target opponent's hand
+        setChoice(playerA, cascader); // exiled
+
+        checkExileCount("cascader", 1, PhaseStep.POSTCOMBAT_MAIN, playerB, cascader, 1);
+
+        castSpell(2, PhaseStep.PRECOMBAT_MAIN, playerB, cascader);
+        setChoice(playerB, true); // yes to cascade
+        addTarget(playerB, playerA); // bolt target
+
+        setStrictChooseMode(true);
+        setStopAt(2, PhaseStep.END_TURN);
+        execute();
+
+        assertTappedCount("Wastes", true, 10);
+        assertLife(playerA, 17);
+    }
+}