Act of Heroism fixes (#3608)

* Adding test case for Act of Heroism

* Fixing Act of Heroism mana cost

* Adding can block additional creature effect that applies to spell/ability target rather than source

* Updating Act of Heroism to use new effect

* Removing redundant assertion, adding some comments

Mage/src/main/java/mage/abilities/effects/common/combat/CanBlockAdditionalCreatureTargetEffect.java

@@ -0,0 +1,84 @@
+package mage.abilities.effects.common.combat;
+
+import mage.abilities.Ability;
+import mage.abilities.effects.ContinuousEffectImpl;
+import mage.constants.Duration;
+import mage.constants.Layer;
+import mage.constants.Outcome;
+import mage.constants.SubLayer;
+import mage.game.Game;
+import mage.game.permanent.Permanent;
+import mage.util.CardUtil;
+
+/**
+ * @author mzulch
+ */
+public class CanBlockAdditionalCreatureTargetEffect extends ContinuousEffectImpl {
+
+    protected int amount;
+
+    public CanBlockAdditionalCreatureTargetEffect() {
+        this(Duration.EndOfTurn, 1);
+    }
+
+    public CanBlockAdditionalCreatureTargetEffect(Duration duration, int amount) {
+        super(duration, Outcome.Benefit);
+        this.amount = amount;
+        staticText = setText();
+    }
+
+    public CanBlockAdditionalCreatureTargetEffect(final CanBlockAdditionalCreatureTargetEffect effect) {
+        super(effect);
+        this.amount = effect.amount;
+    }
+
+    @Override
+    public CanBlockAdditionalCreatureTargetEffect copy() {
+        return new CanBlockAdditionalCreatureTargetEffect(this);
+    }
+
+    @Override
+    public boolean apply(Layer layer, SubLayer sublayer, Ability source, Game game) {
+        Permanent target = game.getPermanent(this.getTargetPointer().getFirst(game, source));
+        if (target == null) {
+            return false;
+        }
+
+        // maxBlocks = 0 equals to "can block any number of creatures"
+        if (amount > 0) {
+            target.setMaxBlocks(target.getMaxBlocks() + amount);
+        } else {
+            target.setMaxBlocks(0);
+        }
+
+        return true;
+    }
+
+    @Override
+    public boolean apply(Game game, Ability source) {
+        return false;
+    }
+
+    private String setText() {
+        String text = "target can block ";
+        switch (amount) {
+            case 0:
+                text += "any number of creatures";
+                break;
+            default:
+                text += CardUtil.numberToText(amount, "an") + " additional creature" + (amount > 1 ? "s" : "");
+        }
+        if (duration == Duration.EndOfTurn) {
+            text += " this turn";
+        }
+        if (duration == Duration.WhileOnBattlefield) {
+            text += " each combat";
+        }
+        return text;
+    }
+
+    @Override
+    public boolean hasLayer(Layer layer) {
+        return layer == Layer.RulesEffects;
+    }
+}