refactor: refined logic

lib/game/pinball_game.dart

@@ -99,12 +99,10 @@ class _GameBallsController extends ComponentController<PinballGame>
 
   @override
   bool listenWhen(GameState? previousState, GameState newState) {
-    final previousBalls =
-        (previousState?.balls ?? 0) + (previousState?.bonusBalls ?? 0);
-    final currentBalls = newState.balls + newState.bonusBalls;
-    final canBallRespawn = newState.balls > 0 && newState.bonusBalls == 0;
+    final noBallsLeft = component.descendants().whereType<Ball>().isEmpty;
+    final canBallRespawn = newState.balls > 0;
 
-    return previousBalls != currentBalls && canBallRespawn;
+    return noBallsLeft && canBallRespawn;
   }
 
   @override

test/game/pinball_game_test.dart

@@ -1,5 +1,7 @@
 // ignore_for_file: cascade_invocations
 
+import 'dart:math';
+
 import 'package:flame/components.dart';
 import 'package:flame/game.dart';
 import 'package:flame_test/flame_test.dart';
@@ -66,42 +68,48 @@ void main() {
         // TODO(alestiago): Write test to be controller agnostic.
         group('listenWhen', () {
           flameTester.test(
-            'listens when a ball is lost and no bonus balls',
+            'listens when all balls are gone and there are more than 0 balls',
             (game) async {
-              const previousState = GameState(
-                score: 0,
-                balls: 3,
-                bonusBalls: 0,
-                activatedBonusLetters: [],
-                bonusHistory: [],
-                activatedDashNests: {},
-              );
-              final newState =
-                  previousState.copyWith(balls: previousState.balls - 1);
+              final newState = MockGameState();
+              when(() => newState.balls).thenReturn(2);
+              game.descendants().whereType<Ball>().forEach(game.remove);
+              await game.ready();
 
               expect(
-                game.controller.listenWhen(previousState, newState),
+                game.controller.listenWhen(MockGameState(), newState),
                 isTrue,
               );
             },
           );
 
           flameTester.test(
-            "doesn't listen when a ball is lost and has bonus balls",
+            "doesn't listen when some balls are left",
             (game) async {
-              const previousState = GameState(
-                score: 0,
-                balls: 3,
-                bonusBalls: 1,
-                activatedBonusLetters: [],
-                bonusHistory: [],
-                activatedDashNests: {},
+              final newState = MockGameState();
+              when(() => newState.balls).thenReturn(2);
+
+              expect(
+                game.descendants().whereType<Ball>().length,
+                greaterThan(0),
+              );
+              expect(
+                game.controller.listenWhen(MockGameState(), newState),
+                isFalse,
               );
-              final newState =
-                  previousState.copyWith(balls: previousState.balls - 1);
+            },
+          );
+
+          flameTester.test(
+            "doesn't listen when no balls left",
+            (game) async {
+              final newState = MockGameState();
+              when(() => newState.balls).thenReturn(0);
+
+              game.descendants().whereType<Ball>().forEach(game.remove);
+              await game.ready();
 
               expect(
-                game.controller.listenWhen(previousState, newState),
+                game.controller.listenWhen(MockGameState(), newState),
                 isFalse,
               );
             },