update ManaMultiMap clear

update ManaPoolTest

forge-game/src/main/java/forge/game/mana/ManaPool.java

@@ -442,6 +442,9 @@ public class ManaPool extends ManaConversionMatrix implements Iterable<Mana> {
         }
 
         public void clear() {
+            for (Map.Entry<K, Collection<V>> entry : storage().entrySet()) {
+                entry.getValue().clear();
+            }
             storage().clear();
         }
 

forge-gui-desktop/src/test/java/forge/FCollectionTest.java

@@ -36,7 +36,7 @@ public class FCollectionTest {
         int i = 0;
         for (Card c : cc) {
             if (i != 3)
-                cc.remove(c);
+                cc.remove(c);  // throws error if the CardCollection not threadsafe
             i++;
         }
         assertEquals(cc.size(), 1);

forge-gui-desktop/src/test/java/forge/ManaPoolTest.java

@@ -19,6 +19,26 @@ public class ManaPoolTest extends SimulationTest {
      * Just a quick test for ManaPool.
      */
     @Test
+    void testManaPoolBadLogic() {
+        Game game = initAndCreateGame();
+        Player p0 = game.getPlayers().get(0);
+        Player p1 = game.getPlayers().get(1);
+        Mana w = new Mana(MagicColor.WHITE, new Card(1, game), null);
+        Mana b = new Mana(MagicColor.BLACK, new Card(1, game), null);
+        p0.getManaPool().addMana(w, false);
+        p0.getManaPool().addMana(w, false);
+        p0.getManaPool().addMana(w, false);
+        p1.getManaPool().addMana(b, false);
+        p1.getManaPool().addMana(b, false);
+        p1.getManaPool().resetPool(); // empty manapool, should clear all values
+        for (Mana m : p0.getManaPool()) {
+            p1.getManaPool().addMana(m, false);
+            p0.getManaPool().removeMana(m, false); // throws error if ManaPool is not threadsafe
+        }
+        assertEquals(p0.getManaPool().getAmountOfColor(MagicColor.WHITE), 0);
+        assertEquals(p1.getManaPool().getAmountOfColor(MagicColor.WHITE), 3);
+    }
+    @Test
     void testCompletableFuture() {
         Game game = initAndCreateGame();
         Player p0 = game.getPlayers().get(0);