Break a 9-clash pet deadlock by fainting both combatants.

internal/game/battle_test.go

@@ -736,3 +736,28 @@ func TestSkunkStripFaintsDebuffedPet(t *testing.T) {
 		t.Fatalf("skunk should win once the stripped pet faints, got %d", res.WinnerSeat)
 	}
 }
+
+// Two pets that block every hit could clash forever; the deadlock rule makes
+// them both faint after 9 clashes so the battle can proceed.
+func TestBattleDeadlockBreaksAfterNineClashes(t *testing.T) {
+	g, _, _ := testGame(t)
+	wall := func(name string) Card {
+		return Card{
+			ID: g.newCardID(), Kind: KindPet, Name: name, Tier: 1, Power: 3, Suit: SuitRed,
+			Effects: []Effect{{Trigger: TriggerPlay, Action: ActionShieldSelf, Count: 20}},
+		}
+	}
+	res := forceBattle(t, g, []Card{wall("Wall")}, []Card{wall("Fort")})
+
+	clashes := eventsOfType(res, "clash")
+	if len(clashes) != 9 {
+		t.Fatalf("deadlock should resolve after 9 clashes, got %d", len(clashes))
+	}
+	last := clashes[len(clashes)-1]
+	if !last.Died[0] || !last.Died[1] {
+		t.Fatalf("the 9th clash should faint both pets: %+v", last)
+	}
+	if res.WinnerSeat != -1 {
+		t.Fatalf("a deadlock is a draw, got winner=%d", res.WinnerSeat)
+	}
+}