REFACTOR: break down the logic into dedicated methods, tests cleaned up

lib/bowling_game.dart

@@ -1,35 +1,58 @@
 class BowlingGame {
+  static const _totalFrames = 10;
+  static const _allPins = 10;
+  static const _rollsInNormalFrame = 2;
+  static const _rollsInStrike = 1;
+
   final List<int> _rolls = [];
 
-  void roll(int pins) {
-    _rolls.add(pins);
-  }
+  void roll(int pins) => _rolls.add(pins);
 
   int score() {
-    int totalScore = 0;
+    int total = 0;
     int rollIndex = 0;
 
-    for (int frame = 0; frame < 10; frame++) {
+    for (int frame = 0; frame < _totalFrames; frame++) {
       if (_isStrike(rollIndex)) {
-        totalScore += 10 + _rolls[rollIndex + 1] + _rolls[rollIndex + 2];
-        rollIndex += 1;
+        total += _strikeScore(rollIndex);
+        rollIndex += _rollsInStrike;
       } else if (_isSpare(rollIndex)) {
-        totalScore += 10 + _rolls[rollIndex + 2];
-        rollIndex += 2;
+        total += _spareScore(rollIndex);
+        rollIndex += _rollsInNormalFrame;
       } else {
-        totalScore += _rolls[rollIndex] + _rolls[rollIndex + 1];
-        rollIndex += 2;
+        total += _normalScore(rollIndex);
+        rollIndex += _rollsInNormalFrame;
       }
     }
 
-    return totalScore;
+    return total;
+  }
+
+  int _strikeScore(int rollIndex) {
+    return _allPins + _nextTwoRollsBonus(rollIndex);
+  }
+
+  int _spareScore(int rollIndex) {
+    return _allPins + _nextRollBonus(rollIndex);
+  }
+
+  int _normalScore(int rollIndex) {
+    return _rolls[rollIndex] + _rolls[rollIndex + 1];
+  }
+
+  int _nextTwoRollsBonus(int rollIndex) {
+    return _rolls[rollIndex + 1] + _rolls[rollIndex + 2];
+  }
+
+  int _nextRollBonus(int rollIndex) {
+    return _rolls[rollIndex + 2];
   }
 
   bool _isSpare(int rollIndex) {
-    return _rolls[rollIndex] + _rolls[rollIndex + 1] == 10;
+    return _rolls[rollIndex] + _rolls[rollIndex + 1] == _allPins;
   }
 
   bool _isStrike(int rollIndex) {
-    return _rolls[rollIndex] == 10;
+    return _rolls[rollIndex] == _allPins;
   }
 }

test/bowling_game_test.dart

@@ -2,7 +2,7 @@ import 'package:tdd_katas/bowling_game.dart';
 import 'package:test/test.dart';
 
 void main() {
-  group('Bowling Game', () {
+  group('Bowling Game Scoring', () {
     late BowlingGame game;
 
     setUp(() {
@@ -15,32 +15,64 @@ void main() {
       }
     }
 
-    test('gutter game - all zeros', () {
+    group('Basic Scoring', () {
+      test('gutter game - no pins knocked', () {
         rollMany(20, 0);
         expect(game.score(), 0);
       });
 
-    test('all ones - score is 20', () {
+      test('all ones - simple addition', () {
         rollMany(20, 1);
         expect(game.score(), 20);
       });
+    });
 
-    test('one spare', () {
+    group('Spare Bonus (next 1 roll)', () {
+      test('one spare in first frame', () {
         game.roll(5);
         game.roll(5); // spare
         game.roll(3); // bonus for spare
-      rollMany(17, 0); // rest are gutter balls
+        rollMany(17, 0);
 
-      expect(game.score(), 16); // 10 (spare) + 3 (bonus) + 3 (normal roll)
+        expect(game.score(), 16); // 10 + 3 (bonus) + 3
       });
 
-    test('one strike', () {
+      test('all spares with 5 pins each', () {
+        rollMany(21, 5); // 10 frames of 5,5 + 1 bonus roll
+        expect(game.score(), 150);
+      });
+    });
+
+    group('Strike Bonus (next 2 rolls)', () {
+      test('one strike in first frame', () {
         game.roll(10); // Strike!
         game.roll(3);
         game.roll(4); // Next 2 rolls are bonus
         rollMany(16, 0);
 
-      expect(game.score(), 24); // 10 + 3 + 4 (strike) + 3 + 4 (frame 2) = 24
+        expect(game.score(), 24); // 10 + 3 + 4 (bonus) + 7
+      });
+
+      test('perfect game - twelve consecutive strikes', () {
+        rollMany(12, 10);
+        expect(game.score(), 300);
+      });
+    });
+
+    group('Complex Scenarios', () {
+      test('combination of strikes, spares, and normal frames', () {
+        game.roll(10); // Frame 1: Strike
+        game.roll(5);
+        game.roll(5); // Frame 2: Spare
+        game.roll(7);
+        game.roll(2); // Frame 3: Normal
+        rollMany(15, 0);
+
+        // Frame 1: 10 + 5 + 5 = 20
+        // Frame 2: 10 + 7 = 17
+        // Frame 3: 7 + 2 = 9
+        expect(game.score(), 46);
+      });
     });
   });
 }