Refactored tests in own files

test/db_tests/player_group_test.dart

@@ -0,0 +1,90 @@
+import 'package:clock/clock.dart';
+import 'package:drift/drift.dart';
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:game_tracker/data/db/database.dart';
+import 'package:game_tracker/data/dto/group.dart';
+import 'package:game_tracker/data/dto/player.dart';
+
+void main() {
+  late AppDatabase database;
+  late Player player1;
+  late Player player2;
+  late Player player3;
+  late Player player4;
+  late Group testgroup;
+  final fixedDate = DateTime(2025, 19, 11, 00, 11, 23);
+  final fakeClock = Clock(() => fixedDate);
+
+  setUp(() {
+    database = AppDatabase(
+      DatabaseConnection(
+        NativeDatabase.memory(),
+        // Recommended for widget tests to avoid test errors.
+        closeStreamsSynchronously: true,
+      ),
+    );
+
+    withClock(fakeClock, () {
+      player1 = Player(name: 'Alice');
+      player2 = Player(name: 'Bob');
+      player3 = Player(name: 'Charlie');
+      player4 = Player(name: 'Diana');
+      testgroup = Group(
+        name: 'Test Group',
+        members: [player1, player2, player3],
+      );
+    });
+  });
+  tearDown(() async {
+    await database.close();
+  });
+
+  group('Player-Group Tests', () {
+    test('Adding a player to a group works correctly', () async {
+      await database.groupDao.addGroup(group: testgroup);
+      await database.playerDao.addPlayer(player: player4);
+      await database.playerGroupDao.addPlayerToGroup(
+        groupId: testgroup.id,
+        player: player4,
+      );
+
+      var playerAdded = await database.playerGroupDao.isPlayerInGroup(
+        groupId: testgroup.id,
+        playerId: player4.id,
+      );
+
+      expect(playerAdded, true);
+
+      playerAdded = await database.playerGroupDao.isPlayerInGroup(
+        groupId: testgroup.id,
+        playerId: '',
+      );
+
+      expect(playerAdded, false);
+    });
+
+    test('Removing player from group works correctly', () async {
+      await database.groupDao.addGroup(group: testgroup);
+
+      final playerToRemove = testgroup.members[0];
+
+      final removed = await database.playerGroupDao.removePlayerFromGroup(
+        playerId: playerToRemove.id,
+        groupId: testgroup.id,
+      );
+      expect(removed, true);
+
+      final result = await database.groupDao.getGroupById(
+        groupId: testgroup.id,
+      );
+      expect(result.members.length, testgroup.members.length - 1);
+
+      final playerExists = result.members.any((p) => p.id == playerToRemove.id);
+      expect(playerExists, false);
+    });
+
+    //TODO: test getPlayersOfGroup()
+    test('Retrieving players of a group works correctly', () async {});
+  });
+}