feat: implemented `InitialPosition` on `BodyComponent`s (#50)

* feat: made Baseboard use InitialPosition

* feat: made Plunger use InitialPosition

* feat: made SlingShot use InitialPosition

* fix: fixed plunger not initialised

* feat: made RoundBumper use InitialPosition

* feat: made Pathway use InitialPosition

* feat: made JointAnchor use InitialPosition

* feat: made BonusWord use InitialPosition

* feat: changed override to onLoad

* feat: made Flipper use InitialPosition

* feat: made Ball use InitialPosition

* feat: made InitialPosition position the body

* feat: included default value

* feat: removed unnecessary positioning

* refactor: removed old test

* refactor: removed unnecessary tests

* refactor: improved assertion message

Co-authored-by: Erick <erickzanardoo@gmail.com>

Co-authored-by: Erick <erickzanardoo@gmail.com>

lib/game/components/ball.dart

@@ -6,14 +6,9 @@ import 'package:pinball/game/game.dart';
 /// A solid, [BodyType.dynamic] sphere that rolls and bounces along the
 /// [PinballGame].
 /// {@endtemplate}
-class Ball extends BodyComponent<PinballGame> {
+class Ball extends BodyComponent<PinballGame> with InitialPosition {
   /// {@macro ball}
-  Ball({
+  Ball();
-    required Vector2 position,
-  }) : _position = position;
-
-  /// The initial position of the [Ball] body.
-  final Vector2 _position;
 
   /// The size of the [Ball]
   final Vector2 size = Vector2.all(2);
@@ -45,7 +40,6 @@ class Ball extends BodyComponent<PinballGame> {
 
     final bodyDef = BodyDef()
       ..userData = this
-      ..position = Vector2(_position.x, _position.y + size.y)
       ..type = BodyType.dynamic;
 
     return world.createBody(bodyDef)..createFixture(fixtureDef);

lib/game/components/baseboard.dart

@@ -6,13 +6,11 @@ import 'package:pinball/game/game.dart';
 /// {@template baseboard}
 /// Straight, angled board piece to corral the [Ball] towards the [Flipper]s.
 /// {@endtemplate}
-class Baseboard extends BodyComponent {
+class Baseboard extends BodyComponent with InitialPosition {
   /// {@macro baseboard}
   Baseboard({
     required BoardSide side,
-    required Vector2 position,
+  }) : _side = side;
-  })  : _side = side,
-        _position = position;
 
   /// The width of the [Baseboard].
   static const width = 10.0;
@@ -20,9 +18,6 @@ class Baseboard extends BodyComponent {
   /// The height of the [Baseboard].
   static const height = 2.0;
 
-  /// The position of the [Baseboard] body.
-  final Vector2 _position;
-
   /// Whether the [Baseboard] is on the left or right side of the board.
   final BoardSide _side;
 
@@ -63,7 +58,6 @@ class Baseboard extends BodyComponent {
     const angle = math.pi / 7;
 
     final bodyDef = BodyDef()
-      ..position = _position
       ..type = BodyType.static
       ..angle = _side.isLeft ? -angle : angle;
 

lib/game/components/board.dart

@@ -59,23 +59,19 @@ class _BottomGroupSide extends Component {
 
     final flipper = Flipper.fromSide(
       side: _side,
-      position: _position,
+    )..initialPosition = _position;
-    );
+    final baseboard = Baseboard(side: _side)
-    final baseboard = Baseboard(
+      ..initialPosition = _position +
-      side: _side,
-      position: _position +
           Vector2(
             (Flipper.width * direction) - direction,
             Flipper.height,
-          ),
           );
     final slingShot = SlingShot(
       side: _side,
-      position: _position +
+    )..initialPosition = _position +
         Vector2(
           (Flipper.width) * direction,
           Flipper.height + SlingShot.size.y,
-          ),
         );
 
     await addAll([flipper, baseboard, slingShot]);

lib/game/components/bonus_word.dart

@@ -74,10 +74,9 @@ class BonusWord extends Component with BlocComponent<GameBloc, GameState> {
       unawaited(
         add(
           BonusLetter(
-            position: _position - Vector2(16 - (i * 6), -30),
             letter: letters[i],
             index: i,
-          ),
+          )..initialPosition = _position - Vector2(16 - (i * 6), -30),
         ),
       );
     }
@@ -89,14 +88,12 @@ class BonusWord extends Component with BlocComponent<GameBloc, GameState> {
 /// which will activate its letter after contact with a [Ball].
 /// {@endtemplate}
 class BonusLetter extends BodyComponent<PinballGame>
-    with BlocComponent<GameBloc, GameState> {
+    with BlocComponent<GameBloc, GameState>, InitialPosition {
   /// {@macro bonus_letter}
   BonusLetter({
-    required Vector2 position,
     required String letter,
     required int index,
-  })  : _position = position,
+  })  : _letter = letter,
-        _letter = letter,
         _index = index {
     paint = Paint()..color = _disableColor;
   }
@@ -107,7 +104,6 @@ class BonusLetter extends BodyComponent<PinballGame>
   static const _activeColor = Colors.green;
   static const _disableColor = Colors.red;
 
-  final Vector2 _position;
   final String _letter;
   final int _index;
 
@@ -134,7 +130,6 @@ class BonusLetter extends BodyComponent<PinballGame>
 
     final bodyDef = BodyDef()
       ..userData = this
-      ..position = _position
       ..type = BodyType.static;
 
     return world.createBody(bodyDef)..createFixture(fixtureDef);

lib/game/components/flipper.dart

@@ -13,19 +13,15 @@ import 'package:pinball/game/game.dart';
 ///
 /// [Flipper] can be controlled by the player in an arc motion.
 /// {@endtemplate flipper}
-class Flipper extends BodyComponent with KeyboardHandler {
+class Flipper extends BodyComponent with KeyboardHandler, InitialPosition {
   /// {@macro flipper}
   Flipper._({
-    required Vector2 position,
     required this.side,
     required List<LogicalKeyboardKey> keys,
-  })  : _position = position,
+  }) : _keys = keys;
-        _keys = keys;
 
-  Flipper._left({
+  Flipper._left()
-    required Vector2 position,
+      : this._(
-  }) : this._(
-          position: position,
           side: BoardSide.left,
           keys: [
             LogicalKeyboardKey.arrowLeft,
@@ -33,10 +29,8 @@ class Flipper extends BodyComponent with KeyboardHandler {
           ],
         );
 
-  Flipper._right({
+  Flipper._right()
-    required Vector2 position,
+      : this._(
-  }) : this._(
-          position: position,
           side: BoardSide.right,
           keys: [
             LogicalKeyboardKey.arrowRight,
@@ -50,13 +44,12 @@ class Flipper extends BodyComponent with KeyboardHandler {
   /// horizontally, also have different [LogicalKeyboardKey]s that control them.
   factory Flipper.fromSide({
     required BoardSide side,
-    required Vector2 position,
   }) {
     switch (side) {
       case BoardSide.left:
-        return Flipper._left(position: position);
+        return Flipper._left();
       case BoardSide.right:
-        return Flipper._right(position: position);
+        return Flipper._right();
     }
   }
 
@@ -82,9 +75,6 @@ class Flipper extends BodyComponent with KeyboardHandler {
   /// whereas a [Flipper] with [BoardSide.right] has a clockwise arc motion.
   final BoardSide side;
 
-  /// The initial position of the [Flipper] body.
-  final Vector2 _position;
-
   /// The [LogicalKeyboardKey]s that will control the [Flipper].
   ///
   /// [onKeyEvent] method listens to when one of these keys is pressed.
@@ -200,9 +190,7 @@ class Flipper extends BodyComponent with KeyboardHandler {
   Body createBody() {
     final bodyDef = BodyDef()
       ..gravityScale = 0
-      ..type = BodyType.dynamic
+      ..type = BodyType.dynamic;
-      ..position = _position;
-
     final body = world.createBody(bodyDef);
     _createFixtureDefs().forEach(body.createFixture);
 
@@ -238,14 +226,14 @@ class FlipperAnchor extends JointAnchor {
   /// {@macro flipper_anchor}
   FlipperAnchor({
     required Flipper flipper,
-  }) : super(
+  }) {
-          position: Vector2(
+    initialPosition = Vector2(
       flipper.side.isLeft
           ? flipper.body.position.x - Flipper.width / 2
           : flipper.body.position.x + Flipper.width / 2,
       flipper.body.position.y,
-          ),
     );
+  }
 }
 
 /// {@template flipper_anchor_revolute_joint_def}

lib/game/components/initial_position.dart

@@ -2,16 +2,28 @@ import 'package:flame_forge2d/flame_forge2d.dart';
 
 /// Forces a given [BodyComponent] to position their [body] to an
 /// [initialPosition].
+///
+/// Note: If the [initialPosition] is set after the [BodyComponent] has been
+/// loaded it will have no effect; defaulting to [Vector2.zero].
 mixin InitialPosition<T extends Forge2DGame> on BodyComponent<T> {
-  /// The initial position of the [body].
+  final Vector2 _initialPosition = Vector2.zero();
-  late final Vector2 initialPosition;
 
-  @override
+  set initialPosition(Vector2 value) {
-  void onMount() {
-    super.onMount();
     assert(
-      body.position == initialPosition,
+      !isLoaded,
-      'Body position is not equal to initial position.',
+      'Cannot set initialPosition after component has already loaded.',
     );
+    if (value == initialPosition) return;
+
+    _initialPosition.setFrom(value);
+  }
+
+  /// The initial position of the [body].
+  Vector2 get initialPosition => _initialPosition;
+
+  @override
+  Future<void> onLoad() async {
+    await super.onLoad();
+    body.position.setFrom(initialPosition);
   }
 }

lib/game/components/joint_anchor.dart

@@ -1,11 +1,12 @@
 import 'package:flame_forge2d/flame_forge2d.dart';
+import 'package:pinball/game/game.dart';
 
 /// {@template joint_anchor}
 /// Non visual [BodyComponent] used to hold a [BodyType.dynamic] in [Joint]s
 /// with this [BodyType.static].
 ///
-/// It is recommended to [_position] the anchor first and then use the body
+/// It is recommended to use [JointAnchor.body.position] to position the anchor
-/// position as the anchor point when initializing a [JointDef].
+/// point when initializing a [JointDef].
 ///
 /// ```dart
 /// initialize(
@@ -15,18 +16,12 @@ import 'package:flame_forge2d/flame_forge2d.dart';
 /// );
 /// ```
 /// {@endtemplate}
-class JointAnchor extends BodyComponent {
+class JointAnchor extends BodyComponent with InitialPosition {
   /// {@macro joint_anchor}
-  JointAnchor({
+  JointAnchor();
-    required Vector2 position,
-  }) : _position = position;
-
-  final Vector2 _position;
 
   @override
   Body createBody() {
-    final bodyDef = BodyDef()..position = _position;
+    return world.createBody(BodyDef());
-
-    return world.createBody(bodyDef);
   }
 }

lib/game/components/pathway.dart

@@ -2,20 +2,19 @@ import 'package:flame/extensions.dart';
 import 'package:flame_forge2d/flame_forge2d.dart';
 import 'package:flutter/material.dart';
 import 'package:geometry/geometry.dart';
+import 'package:pinball/game/game.dart';
 
 /// {@template pathway}
 /// [Pathway] creates lines of various shapes.
 ///
 /// [BodyComponent]s such as a Ball can collide and move along a [Pathway].
 /// {@endtemplate}
-class Pathway extends BodyComponent {
+class Pathway extends BodyComponent with InitialPosition {
   Pathway._({
     // TODO(ruialonso): remove color when assets added.
     Color? color,
-    required Vector2 position,
     required List<List<Vector2>> paths,
-  })  : _position = position,
+  }) : _paths = paths {
-        _paths = paths {
     paint = Paint()
       ..color = color ?? const Color.fromARGB(0, 0, 0, 0)
       ..style = PaintingStyle.stroke;
@@ -23,14 +22,12 @@ class Pathway extends BodyComponent {
 
   /// Creates a uniform unidirectional (straight) [Pathway].
   ///
-  /// Does so with two [ChainShape] separated by a [width]. Placed
+  /// Does so with two [ChainShape] separated by a [width]. Can
-  /// at a [position] between [start] and [end] points. Can
   /// be rotated by a given [rotation] in radians.
   ///
   /// If [singleWall] is true, just one [ChainShape] is created.
   factory Pathway.straight({
     Color? color,
-    required Vector2 position,
     required Vector2 start,
     required Vector2 end,
     required double width,
@@ -56,28 +53,25 @@ class Pathway extends BodyComponent {
 
     return Pathway._(
       color: color,
-      position: position,
       paths: paths,
     );
   }
 
   /// Creates an arc [Pathway].
   ///
-  /// The [angle], in radians, specifies the size of the arc. For example, 2*pi
+  /// The [angle], in radians, specifies the size of the arc. For example, two
-  /// returns a complete circumference and minor angles a semi circumference.
+  /// pi returns a complete circumference.
-  ///
-  /// The center of the arc is placed at [position].
   ///
   /// Does so with two [ChainShape] separated by a [width]. Which can be
   /// rotated by a given [rotation] in radians.
   ///
   /// The outer radius is specified by [radius], whilst the inner one is
-  /// equivalent to [radius] - [width].
+  /// equivalent to the [radius] minus the [width].
   ///
   /// If [singleWall] is true, just one [ChainShape] is created.
   factory Pathway.arc({
     Color? color,
-    required Vector2 position,
+    required Vector2 center,
     required double width,
     required double radius,
     required double angle,
@@ -88,7 +82,7 @@ class Pathway extends BodyComponent {
 
     // TODO(ruialonso): Refactor repetitive logic
     final outerWall = calculateArc(
-      center: position,
+      center: center,
       radius: radius,
       angle: angle,
       offsetAngle: rotation,
@@ -97,7 +91,7 @@ class Pathway extends BodyComponent {
 
     if (!singleWall) {
       final innerWall = calculateArc(
-        center: position,
+        center: center,
         radius: radius - width,
         angle: angle,
         offsetAngle: rotation,
@@ -107,7 +101,6 @@ class Pathway extends BodyComponent {
 
     return Pathway._(
       color: color,
-      position: position,
       paths: paths,
     );
   }
@@ -123,7 +116,6 @@ class Pathway extends BodyComponent {
   /// If [singleWall] is true, just one [ChainShape] is created.
   factory Pathway.bezierCurve({
     Color? color,
-    required Vector2 position,
     required List<Vector2> controlPoints,
     required double width,
     double rotation = 0,
@@ -148,20 +140,15 @@ class Pathway extends BodyComponent {
 
     return Pathway._(
       color: color,
-      position: position,
       paths: paths,
     );
   }
 
-  final Vector2 _position;
   final List<List<Vector2>> _paths;
 
   @override
   Body createBody() {
-    final bodyDef = BodyDef()
+    final bodyDef = BodyDef()..type = BodyType.static;
-      ..type = BodyType.static
-      ..position = _position;
-
     final body = world.createBody(bodyDef);
     for (final path in _paths) {
       final chain = ChainShape()

lib/game/components/plunger.dart

@@ -9,15 +9,11 @@ import 'package:pinball/game/game.dart';
 ///
 /// [Plunger] ignores gravity so the player controls its downward [_pull].
 /// {@endtemplate}
-class Plunger extends BodyComponent with KeyboardHandler {
+class Plunger extends BodyComponent with KeyboardHandler, InitialPosition {
   /// {@macro plunger}
   Plunger({
-    required Vector2 position,
     required this.compressionDistance,
-  }) : _position = position;
+  });
-
-  /// The initial position of the [Plunger] body.
-  final Vector2 _position;
 
   /// Distance the plunger can lower.
   final double compressionDistance;
@@ -30,7 +26,6 @@ class Plunger extends BodyComponent with KeyboardHandler {
 
     final bodyDef = BodyDef()
       ..userData = this
-      ..position = _position
       ..type = BodyType.dynamic
       ..gravityScale = 0;
 
@@ -45,9 +40,9 @@ class Plunger extends BodyComponent with KeyboardHandler {
   /// Set an upward velocity on the [Plunger].
   ///
   /// The velocity's magnitude depends on how far the [Plunger] has been pulled
-  /// from its original [_position].
+  /// from its original [initialPosition].
   void _release() {
-    final velocity = (_position.y - body.position.y) * 9;
+    final velocity = (initialPosition.y - body.position.y) * 9;
     body.linearVelocity = Vector2(0, velocity);
   }
 
@@ -102,12 +97,12 @@ class PlungerAnchor extends JointAnchor {
   /// {@macro plunger_anchor}
   PlungerAnchor({
     required Plunger plunger,
-  }) : super(
+  }) {
-          position: Vector2(
+    initialPosition = Vector2(
       plunger.body.position.x,
       plunger.body.position.y - plunger.compressionDistance,
-          ),
     );
+  }
 }
 
 /// {@template plunger_anchor_prismatic_joint_def}

lib/game/components/round_bumper.dart

@@ -4,19 +4,14 @@ import 'package:pinball/game/game.dart';
 /// {@template round_bumper}
 /// Circular body that repels a [Ball] on contact, increasing the score.
 /// {@endtemplate}
-class RoundBumper extends BodyComponent with ScorePoints {
+class RoundBumper extends BodyComponent with ScorePoints, InitialPosition {
   /// {@macro round_bumper}
   RoundBumper({
-    required Vector2 position,
     required double radius,
     required int points,
-  })  : _position = position,
+  })  : _radius = radius,
-        _radius = radius,
         _points = points;
 
-  /// The position of the [RoundBumper] body.
-  final Vector2 _position;
-
   /// The radius of the [RoundBumper].
   final double _radius;
 
@@ -32,9 +27,7 @@ class RoundBumper extends BodyComponent with ScorePoints {
 
     final fixtureDef = FixtureDef(shape)..restitution = 1;
 
-    final bodyDef = BodyDef()
+    final bodyDef = BodyDef()..type = BodyType.static;
-      ..position = _position
-      ..type = BodyType.static;
 
     return world.createBody(bodyDef)..createFixture(fixtureDef);
   }

lib/game/components/sling_shot.dart

@@ -10,22 +10,17 @@ import 'package:pinball/game/game.dart';
 ///
 /// [SlingShot]s are usually positioned above each [Flipper].
 /// {@endtemplate sling_shot}
-class SlingShot extends BodyComponent {
+class SlingShot extends BodyComponent with InitialPosition {
   /// {@macro sling_shot}
   SlingShot({
-    required Vector2 position,
     required BoardSide side,
-  })  : _position = position,
+  }) : _side = side {
-        _side = side {
     // TODO(alestiago): Use sprite instead of color when provided.
     paint = Paint()
       ..color = const Color(0xFF00FF00)
       ..style = PaintingStyle.fill;
   }
 
-  /// The initial position of the [SlingShot] body.
-  final Vector2 _position;
-
   /// Whether the [SlingShot] is on the left or right side of the board.
   ///
   /// A [SlingShot] with [BoardSide.left] propels the [Ball] to the right,
@@ -88,8 +83,7 @@ class SlingShot extends BodyComponent {
 
   @override
   Body createBody() {
-    final bodyDef = BodyDef()..position = _position;
+    final body = world.createBody(BodyDef());
-    final body = world.createBody(bodyDef);
     _createFixtureDefs().forEach(body.createFixture);
 
     return body;

lib/game/pinball_game.dart

@@ -78,7 +78,11 @@ class PinballGame extends Forge2DGame
   }
 
   void spawnBall() {
-    add(Ball(position: plunger.body.position));
+    final ball = Ball();
+    add(
+      ball
+        ..initialPosition = plunger.body.position + Vector2(0, ball.size.y / 2),
+    );
   }
 
   void _addContactCallbacks() {
@@ -93,19 +97,17 @@ class PinballGame extends Forge2DGame
   }
 
   Future<void> _addPlunger() async {
-    final compressionDistance = camera.viewport.effectiveSize.y / 12;
-
-    await add(
     plunger = Plunger(
-        position: screenToWorld(
+      compressionDistance: camera.viewport.effectiveSize.y / 12,
+    );
+    plunger.initialPosition = screenToWorld(
       Vector2(
         camera.viewport.effectiveSize.x / 1.035,
-            camera.viewport.effectiveSize.y - compressionDistance,
+        camera.viewport.effectiveSize.y - plunger.compressionDistance,
-          ),
-        ),
-        compressionDistance: compressionDistance,
       ),
     );
+
+    await add(plunger);
   }
 }
 
@@ -114,6 +116,8 @@ class DebugPinballGame extends PinballGame with TapDetector {
 
   @override
   void onTapUp(TapUpInfo info) {
-    add(Ball(position: info.eventPosition.game));
+    add(
+      Ball()..initialPosition = info.eventPosition.game,
+    );
   }
 }

test/game/components/ball_test.dart

@@ -17,7 +17,7 @@ void main() {
     flameTester.test(
       'loads correctly',
       (game) async {
-        final ball = Ball(position: Vector2.zero());
+        final ball = Ball();
         await game.ready();
         await game.ensureAdd(ball);
 
@@ -26,26 +26,10 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          final position = Vector2.all(10);
-          final ball = Ball(position: position);
-          await game.ensureAdd(ball);
-          game.contains(ball);
-
-          final expectedPosition = Vector2(
-            position.x,
-            position.y + ball.size.y,
-          );
-          expect(ball.body.position, equals(expectedPosition));
-        },
-      );
-
       flameTester.test(
         'is dynamic',
         (game) async {
-          final ball = Ball(position: Vector2.zero());
+          final ball = Ball();
           await game.ensureAdd(ball);
 
           expect(ball.body.bodyType, equals(BodyType.dynamic));
@@ -57,7 +41,7 @@ void main() {
       flameTester.test(
         'exists',
         (game) async {
-          final ball = Ball(position: Vector2.zero());
+          final ball = Ball();
           await game.ensureAdd(ball);
 
           expect(ball.body.fixtures[0], isA<Fixture>());
@@ -67,7 +51,7 @@ void main() {
       flameTester.test(
         'is dense',
         (game) async {
-          final ball = Ball(position: Vector2.zero());
+          final ball = Ball();
           await game.ensureAdd(ball);
 
           final fixture = ball.body.fixtures[0];
@@ -78,7 +62,7 @@ void main() {
       flameTester.test(
         'shape is circular',
         (game) async {
-          final ball = Ball(position: Vector2.zero());
+          final ball = Ball();
           await game.ensureAdd(ball);
 
           final fixture = ball.body.fixtures[0];

test/game/components/baseboard_test.dart

@@ -15,13 +15,12 @@ void main() {
       (game) async {
         await game.ready();
         final leftBaseboard = Baseboard(
-          position: Vector2.zero(),
           side: BoardSide.left,
         );
         final rightBaseboard = Baseboard(
-          position: Vector2.zero(),
           side: BoardSide.right,
         );
+
         await game.ensureAddAll([leftBaseboard, rightBaseboard]);
 
         expect(game.contains(leftBaseboard), isTrue);
@@ -30,28 +29,13 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          final position = Vector2.all(10);
-          final baseboard = Baseboard(
-            position: position,
-            side: BoardSide.left,
-          );
-          await game.ensureAdd(baseboard);
-          game.contains(baseboard);
-
-          expect(baseboard.body.position, position);
-        },
-      );
-
       flameTester.test(
         'is static',
         (game) async {
           final baseboard = Baseboard(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
+
           await game.ensureAdd(baseboard);
 
           expect(baseboard.body.bodyType, equals(BodyType.static));
@@ -62,11 +46,9 @@ void main() {
         'is at an angle',
         (game) async {
           final leftBaseboard = Baseboard(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           final rightBaseboard = Baseboard(
-            position: Vector2.zero(),
             side: BoardSide.right,
           );
           await game.ensureAddAll([leftBaseboard, rightBaseboard]);
@@ -82,7 +64,6 @@ void main() {
         'has three',
         (game) async {
           final baseboard = Baseboard(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(baseboard);

test/game/components/bonus_word_test.dart

@@ -123,7 +123,6 @@ void main() {
       'loads correctly',
       (game) async {
         final bonusLetter = BonusLetter(
-          position: Vector2.zero(),
           letter: 'G',
           index: 0,
         );
@@ -135,27 +134,10 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          final position = Vector2.all(10);
-          final bonusLetter = BonusLetter(
-            position: position,
-            letter: 'G',
-            index: 0,
-          );
-          await game.ensureAdd(bonusLetter);
-          game.contains(bonusLetter);
-
-          expect(bonusLetter.body.position, position);
-        },
-      );
-
       flameTester.test(
         'is static',
         (game) async {
           final bonusLetter = BonusLetter(
-            position: Vector2.zero(),
             letter: 'G',
             index: 0,
           );
@@ -171,7 +153,6 @@ void main() {
         'exists',
         (game) async {
           final bonusLetter = BonusLetter(
-            position: Vector2.zero(),
             letter: 'G',
             index: 0,
           );
@@ -185,7 +166,6 @@ void main() {
         'is sensor',
         (game) async {
           final bonusLetter = BonusLetter(
-            position: Vector2.zero(),
             letter: 'G',
             index: 0,
           );
@@ -200,7 +180,6 @@ void main() {
         'shape is circular',
         (game) async {
           final bonusLetter = BonusLetter(
-            position: Vector2.zero(),
             letter: 'G',
             index: 0,
           );

test/game/components/flipper_test.dart

@@ -22,11 +22,9 @@ void main() {
         (game) async {
           final leftFlipper = Flipper.fromSide(
             side: BoardSide.left,
-            position: Vector2.zero(),
           );
           final rightFlipper = Flipper.fromSide(
             side: BoardSide.right,
-            position: Vector2.zero(),
           );
           await game.ready();
           await game.ensureAddAll([leftFlipper, rightFlipper]);
@@ -40,41 +38,23 @@ void main() {
         test('sets BoardSide', () {
           final leftFlipper = Flipper.fromSide(
             side: BoardSide.left,
-            position: Vector2.zero(),
           );
 
           expect(leftFlipper.side, equals(leftFlipper.side));
 
           final rightFlipper = Flipper.fromSide(
             side: BoardSide.right,
-            position: Vector2.zero(),
           );
           expect(rightFlipper.side, equals(rightFlipper.side));
         });
       });
 
       group('body', () {
-        flameTester.test(
-          'positions correctly',
-          (game) async {
-            final position = Vector2.all(10);
-            final flipper = Flipper.fromSide(
-              side: BoardSide.left,
-              position: position,
-            );
-            await game.ensureAdd(flipper);
-            game.contains(flipper);
-
-            expect(flipper.body.position, position);
-          },
-        );
-
         flameTester.test(
           'is dynamic',
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -87,7 +67,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -100,9 +79,8 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
-            final ball = Ball(position: Vector2.zero());
+            final ball = Ball();
 
             await game.ready();
             await game.ensureAddAll([flipper, ball]);
@@ -121,7 +99,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -134,7 +111,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -165,7 +141,6 @@ void main() {
           setUp(() {
             flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
           });
 
@@ -232,7 +207,6 @@ void main() {
           setUp(() {
             flipper = Flipper.fromSide(
               side: BoardSide.right,
-              position: Vector2.zero(),
             );
           });
 
@@ -302,7 +276,6 @@ void main() {
       (game) async {
         final flipper = Flipper.fromSide(
           side: BoardSide.left,
-          position: Vector2.zero(),
         );
         await game.ensureAdd(flipper);
 
@@ -318,7 +291,6 @@ void main() {
       (game) async {
         final flipper = Flipper.fromSide(
           side: BoardSide.right,
-          position: Vector2.zero(),
         );
         await game.ensureAdd(flipper);
 
@@ -337,7 +309,6 @@ void main() {
         (game) async {
           final flipper = Flipper.fromSide(
             side: BoardSide.left,
-            position: Vector2.zero(),
           );
           await game.ensureAdd(flipper);
 
@@ -359,7 +330,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -380,7 +350,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.right,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -406,7 +375,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.left,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 
@@ -433,7 +401,6 @@ void main() {
           (game) async {
             final flipper = Flipper.fromSide(
               side: BoardSide.right,
-              position: Vector2.zero(),
             );
             await game.ensureAdd(flipper);
 

test/game/components/initial_position_test.dart

@@ -12,13 +12,6 @@ class TestBodyComponent extends BodyComponent with InitialPosition {
   }
 }
 
-class TestPositionedBodyComponent extends BodyComponent with InitialPosition {
-  @override
-  Body createBody() {
-    return world.createBody(BodyDef()..position = initialPosition);
-  }
-}
-
 void main() {
   final flameTester = FlameTester(Forge2DGame.new);
   group('InitialPosition', () {
@@ -27,37 +20,36 @@ void main() {
       expect(component.initialPosition, Vector2(1, 2));
     });
 
-    test('can only be set once', () {
+    flameTester.test(
-      final component = TestBodyComponent()..initialPosition = Vector2(1, 2);
+      'positions correctly',
-      expect(
+      (game) async {
-        () => component.initialPosition = Vector2(3, 4),
+        final position = Vector2.all(10);
-        throwsA(isA<Error>()),
+        final component = TestBodyComponent()..initialPosition = position;
+        await game.ensureAdd(component);
+        expect(component.body.position, equals(position));
+      },
     );
-    });
 
     flameTester.test(
-      'returns normally '
+      'deafaults to zero '
-      'when the body sets the position to initial position',
+      'when no initialPosition is given',
       (game) async {
-        final component = TestPositionedBodyComponent()
+        final component = TestBodyComponent();
-          ..initialPosition = Vector2.zero();
+        await game.ensureAdd(component);
-
+        expect(component.body.position, equals(Vector2.zero()));
-        await expectLater(
-          () async => game.ensureAdd(component),
-          returnsNormally,
-        );
       },
     );
 
     flameTester.test(
-      'throws AssertionError '
+      'setting throws AssertionError '
-      'when not setting initialPosition to body',
+      'when component has loaded',
       (game) async {
-        final component = TestBodyComponent()..initialPosition = Vector2.zero();
+        final component = TestBodyComponent();
         await game.ensureAdd(component);
 
-        await expectLater(
+        expect(component.isLoaded, isTrue);
-          () async => game.ensureAdd(component),
+        expect(
+          () => component.initialPosition = Vector2.all(4),
           throwsAssertionError,
         );
       },

test/game/components/joint_anchor_test.dart

@@ -13,7 +13,7 @@ void main() {
     flameTester.test(
       'loads correctly',
       (game) async {
-        final anchor = JointAnchor(position: Vector2.zero());
+        final anchor = JointAnchor();
         await game.ready();
         await game.ensureAdd(anchor);
 
@@ -22,24 +22,11 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          await game.ready();
-          final position = Vector2.all(10);
-          final anchor = JointAnchor(position: position);
-          await game.ensureAdd(anchor);
-          game.contains(anchor);
-
-          expect(anchor.body.position, position);
-        },
-      );
-
       flameTester.test(
         'is static',
         (game) async {
           await game.ready();
-          final anchor = JointAnchor(position: Vector2.zero());
+          final anchor = JointAnchor();
           await game.ensureAdd(anchor);
 
           expect(anchor.body.bodyType, equals(BodyType.static));
@@ -51,7 +38,7 @@ void main() {
       flameTester.test(
         'has none',
         (game) async {
-          final anchor = JointAnchor(position: Vector2.zero());
+          final anchor = JointAnchor();
           await game.ensureAdd(anchor);
 
           expect(anchor.body.fixtures, isEmpty);

test/game/components/pathway_test.dart

@@ -20,7 +20,6 @@ void main() {
           (game) async {
             await game.ready();
             final pathway = Pathway.straight(
-              position: Vector2.zero(),
               start: Vector2(10, 10),
               end: Vector2(20, 20),
               width: width,
@@ -44,7 +43,6 @@ void main() {
 
             final pathway = Pathway.straight(
               color: defaultColor,
-              position: Vector2.zero(),
               start: Vector2(10, 10),
               end: Vector2(20, 20),
               width: width,
@@ -63,7 +61,6 @@ void main() {
         (game) async {
           await game.ready();
           final pathway = Pathway.straight(
-            position: Vector2.zero(),
             start: Vector2(10, 10),
             end: Vector2(20, 20),
             width: width,
@@ -75,30 +72,11 @@ void main() {
       );
 
       group('body', () {
-        flameTester.test(
-          'positions correctly',
-          (game) async {
-            await game.ready();
-            final position = Vector2.all(10);
-            final pathway = Pathway.straight(
-              position: position,
-              start: Vector2(10, 10),
-              end: Vector2(20, 20),
-              width: width,
-            );
-            await game.ensureAdd(pathway);
-
-            game.contains(pathway);
-            expect(pathway.body.position, position);
-          },
-        );
-
         flameTester.test(
           'is static',
           (game) async {
             await game.ready();
             final pathway = Pathway.straight(
-              position: Vector2.zero(),
               start: Vector2(10, 10),
               end: Vector2(20, 20),
               width: width,
@@ -116,7 +94,6 @@ void main() {
           (game) async {
             await game.ready();
             final pathway = Pathway.straight(
-              position: Vector2.zero(),
               start: Vector2(10, 10),
               end: Vector2(20, 20),
               width: width,
@@ -136,7 +113,6 @@ void main() {
           (game) async {
             await game.ready();
             final pathway = Pathway.straight(
-              position: Vector2.zero(),
               start: Vector2(10, 10),
               end: Vector2(20, 20),
               width: width,
@@ -159,7 +135,7 @@ void main() {
         (game) async {
           await game.ready();
           final pathway = Pathway.arc(
-            position: Vector2.zero(),
+            center: Vector2.zero(),
             width: width,
             radius: 100,
             angle: math.pi / 2,
@@ -171,30 +147,12 @@ void main() {
       );
 
       group('body', () {
-        flameTester.test(
-          'positions correctly',
-          (game) async {
-            await game.ready();
-            final position = Vector2.all(10);
-            final pathway = Pathway.arc(
-              position: position,
-              width: width,
-              radius: 100,
-              angle: math.pi / 2,
-            );
-            await game.ensureAdd(pathway);
-
-            game.contains(pathway);
-            expect(pathway.body.position, position);
-          },
-        );
-
         flameTester.test(
           'is static',
           (game) async {
             await game.ready();
             final pathway = Pathway.arc(
-              position: Vector2.zero(),
+              center: Vector2.zero(),
               width: width,
               radius: 100,
               angle: math.pi / 2,
@@ -220,7 +178,6 @@ void main() {
         (game) async {
           await game.ready();
           final pathway = Pathway.bezierCurve(
-            position: Vector2.zero(),
             controlPoints: controlPoints,
             width: width,
           );
@@ -231,29 +188,11 @@ void main() {
       );
 
       group('body', () {
-        flameTester.test(
-          'positions correctly',
-          (game) async {
-            await game.ready();
-            final position = Vector2.all(10);
-            final pathway = Pathway.bezierCurve(
-              position: position,
-              controlPoints: controlPoints,
-              width: width,
-            );
-            await game.ensureAdd(pathway);
-
-            game.contains(pathway);
-            expect(pathway.body.position, position);
-          },
-        );
-
         flameTester.test(
           'is static',
           (game) async {
             await game.ready();
             final pathway = Pathway.bezierCurve(
-              position: Vector2.zero(),
               controlPoints: controlPoints,
               width: width,
             );

test/game/components/plunger_test.dart

@@ -23,7 +23,6 @@ void main() {
       (game) async {
         await game.ready();
         final plunger = Plunger(
-          position: Vector2.zero(),
           compressionDistance: compressionDistance,
         );
         await game.ensureAdd(plunger);
@@ -33,26 +32,10 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          final position = Vector2.all(10);
-          final plunger = Plunger(
-            position: position,
-            compressionDistance: compressionDistance,
-          );
-          await game.ensureAdd(plunger);
-          game.contains(plunger);
-
-          expect(plunger.body.position, position);
-        },
-      );
-
       flameTester.test(
         'is dynamic',
         (game) async {
           final plunger = Plunger(
-            position: Vector2.zero(),
             compressionDistance: compressionDistance,
           );
           await game.ensureAdd(plunger);
@@ -65,7 +48,6 @@ void main() {
         'ignores gravity',
         (game) async {
           final plunger = Plunger(
-            position: Vector2.zero(),
             compressionDistance: compressionDistance,
           );
           await game.ensureAdd(plunger);
@@ -80,7 +62,6 @@ void main() {
         'exists',
         (game) async {
           final plunger = Plunger(
-            position: Vector2.zero(),
             compressionDistance: compressionDistance,
           );
           await game.ensureAdd(plunger);
@@ -93,7 +74,6 @@ void main() {
         'shape is a polygon',
         (game) async {
           final plunger = Plunger(
-            position: Vector2.zero(),
             compressionDistance: compressionDistance,
           );
           await game.ensureAdd(plunger);
@@ -107,7 +87,6 @@ void main() {
         'has density',
         (game) async {
           final plunger = Plunger(
-            position: Vector2.zero(),
             compressionDistance: compressionDistance,
           );
           await game.ensureAdd(plunger);
@@ -129,7 +108,6 @@ void main() {
 
       setUp(() {
         plunger = Plunger(
-          position: Vector2.zero(),
           compressionDistance: compressionDistance,
         );
       });
@@ -194,7 +172,6 @@ void main() {
       'position is a compression distance below the Plunger',
       (game) async {
         final plunger = Plunger(
-          position: Vector2.zero(),
           compressionDistance: compressionDistance,
         );
         await game.ensureAdd(plunger);
@@ -222,7 +199,6 @@ void main() {
         initialState: const GameState.initial(),
       );
       plunger = Plunger(
-        position: Vector2.zero(),
         compressionDistance: compressionDistance,
       );
     });

test/game/components/round_bumper_test.dart

@@ -18,7 +18,6 @@ void main() {
       (game) async {
         await game.ready();
         final roundBumper = RoundBumper(
-          position: Vector2.zero(),
           radius: radius,
           points: points,
         );
@@ -32,7 +31,6 @@ void main() {
       'has points',
       (game) async {
         final roundBumper = RoundBumper(
-          position: Vector2.zero(),
           radius: radius,
           points: points,
         );
@@ -43,27 +41,10 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          final position = Vector2.all(10);
-          final roundBumper = RoundBumper(
-            position: position,
-            radius: radius,
-            points: points,
-          );
-          await game.ensureAdd(roundBumper);
-          game.contains(roundBumper);
-
-          expect(roundBumper.body.position, equals(position));
-        },
-      );
-
       flameTester.test(
         'is static',
         (game) async {
           final roundBumper = RoundBumper(
-            position: Vector2.zero(),
             radius: radius,
             points: points,
           );
@@ -79,7 +60,6 @@ void main() {
         'exists',
         (game) async {
           final roundBumper = RoundBumper(
-            position: Vector2.zero(),
             radius: radius,
             points: points,
           );
@@ -93,7 +73,6 @@ void main() {
         'has restitution',
         (game) async {
           final roundBumper = RoundBumper(
-            position: Vector2.zero(),
             radius: radius,
             points: points,
           );
@@ -108,7 +87,6 @@ void main() {
         'shape is circular',
         (game) async {
           final roundBumper = RoundBumper(
-            position: Vector2.zero(),
             radius: radius,
             points: points,
           );

test/game/components/sling_shot_test.dart

@@ -13,7 +13,6 @@ void main() {
       'loads correctly',
       (game) async {
         final slingShot = SlingShot(
-          position: Vector2.zero(),
           side: BoardSide.left,
         );
         await game.ensureAdd(slingShot);
@@ -23,25 +22,10 @@ void main() {
     );
 
     group('body', () {
-      flameTester.test(
-        'positions correctly',
-        (game) async {
-          final position = Vector2.all(10);
-          final slingShot = SlingShot(
-            position: position,
-            side: BoardSide.left,
-          );
-          await game.ensureAdd(slingShot);
-
-          expect(slingShot.body.position, equals(position));
-        },
-      );
-
       flameTester.test(
         'is static',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -56,7 +40,6 @@ void main() {
         'exists',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -69,7 +52,6 @@ void main() {
         'shape is triangular',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -85,11 +67,9 @@ void main() {
         'when side is left or right',
         (game) async {
           final leftSlingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           final rightSlingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.right,
           );
 
@@ -109,7 +89,6 @@ void main() {
         'has no friction',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -125,7 +104,6 @@ void main() {
         'exists',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -138,7 +116,6 @@ void main() {
         'shape is edge',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -152,7 +129,6 @@ void main() {
         'has restitution',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);
@@ -166,7 +142,6 @@ void main() {
         'has no friction',
         (game) async {
           final slingShot = SlingShot(
-            position: Vector2.zero(),
             side: BoardSide.left,
           );
           await game.ensureAdd(slingShot);