diff --git a/test/db_tests/player_group_test.dart b/test/db_tests/player_group_test.dart
index 660b066..8959092 100644
--- a/test/db_tests/player_group_test.dart
+++ b/test/db_tests/player_group_test.dart
@@ -100,5 +100,212 @@ void main() {
         expect(players[i].createdAt, testGroup.members[i].createdAt);
       }
     });
+
+    // Verifies that isPlayerInGroup returns false for non-existent player.
+    test('isPlayerInGroup returns false for non-existent player', () async {
+      await database.groupDao.addGroup(group: testGroup);
+
+      final result = await database.playerGroupDao.isPlayerInGroup(
+        playerId: 'non-existent-player-id',
+        groupId: testGroup.id,
+      );
+
+      expect(result, false);
+    });
+
+    // Verifies that isPlayerInGroup returns false for non-existent group.
+    test('isPlayerInGroup returns false for non-existent group', () async {
+      await database.playerDao.addPlayer(player: testPlayer1);
+
+      final result = await database.playerGroupDao.isPlayerInGroup(
+        playerId: testPlayer1.id,
+        groupId: 'non-existent-group-id',
+      );
+
+      expect(result, false);
+    });
+
+    // Verifies that addPlayerToGroup returns false when player already in group.
+    test('addPlayerToGroup returns false when player already in group', () async {
+      await database.groupDao.addGroup(group: testGroup);
+
+      // testPlayer1 is already in testGroup via group creation
+      final result = await database.playerGroupDao.addPlayerToGroup(
+        player: testPlayer1,
+        groupId: testGroup.id,
+      );
+
+      expect(result, false);
+    });
+
+    // Verifies that addPlayerToGroup adds player to player table if not exists.
+    test('addPlayerToGroup adds player to player table if not exists', () async {
+      await database.groupDao.addGroup(group: testGroup);
+
+      // testPlayer4 is not in the database yet
+      var playerExists = await database.playerDao.playerExists(
+        playerId: testPlayer4.id,
+      );
+      expect(playerExists, false);
+
+      await database.playerGroupDao.addPlayerToGroup(
+        player: testPlayer4,
+        groupId: testGroup.id,
+      );
+
+      // Now player should exist in player table
+      playerExists = await database.playerDao.playerExists(
+        playerId: testPlayer4.id,
+      );
+      expect(playerExists, true);
+    });
+
+    // Verifies that removePlayerFromGroup returns false for non-existent player.
+    test('removePlayerFromGroup returns false for non-existent player', () async {
+      await database.groupDao.addGroup(group: testGroup);
+
+      final result = await database.playerGroupDao.removePlayerFromGroup(
+        playerId: 'non-existent-player-id',
+        groupId: testGroup.id,
+      );
+
+      expect(result, false);
+    });
+
+    // Verifies that removePlayerFromGroup returns false for non-existent group.
+    test('removePlayerFromGroup returns false for non-existent group', () async {
+      await database.playerDao.addPlayer(player: testPlayer1);
+
+      final result = await database.playerGroupDao.removePlayerFromGroup(
+        playerId: testPlayer1.id,
+        groupId: 'non-existent-group-id',
+      );
+
+      expect(result, false);
+    });
+
+    // Verifies that getPlayersOfGroup returns empty list for group with no members.
+    test('getPlayersOfGroup returns empty list for empty group', () async {
+      final emptyGroup = Group(name: 'Empty Group', members: []);
+      await database.groupDao.addGroup(group: emptyGroup);
+
+      final players = await database.playerGroupDao.getPlayersOfGroup(
+        groupId: emptyGroup.id,
+      );
+
+      expect(players, isEmpty);
+    });
+
+    // Verifies that getPlayersOfGroup returns empty list for non-existent group.
+    test('getPlayersOfGroup returns empty list for non-existent group', () async {
+      final players = await database.playerGroupDao.getPlayersOfGroup(
+        groupId: 'non-existent-group-id',
+      );
+
+      expect(players, isEmpty);
+    });
+
+    // Verifies that removing all players from a group leaves the group empty.
+    test('Removing all players from a group leaves group empty', () async {
+      await database.groupDao.addGroup(group: testGroup);
+
+      for (final player in testGroup.members) {
+        await database.playerGroupDao.removePlayerFromGroup(
+          playerId: player.id,
+          groupId: testGroup.id,
+        );
+      }
+
+      final players = await database.playerGroupDao.getPlayersOfGroup(
+        groupId: testGroup.id,
+      );
+      expect(players, isEmpty);
+
+      // Group should still exist
+      final groupExists = await database.groupDao.groupExists(
+        groupId: testGroup.id,
+      );
+      expect(groupExists, true);
+    });
+
+    // Verifies that a player can be in multiple groups.
+    test('Player can be in multiple groups', () async {
+      final secondGroup = Group(name: 'Second Group', members: []);
+      await database.groupDao.addGroup(group: testGroup);
+      await database.groupDao.addGroup(group: secondGroup);
+
+      // Add testPlayer1 to second group (already in testGroup)
+      await database.playerGroupDao.addPlayerToGroup(
+        player: testPlayer1,
+        groupId: secondGroup.id,
+      );
+
+      final inFirstGroup = await database.playerGroupDao.isPlayerInGroup(
+        playerId: testPlayer1.id,
+        groupId: testGroup.id,
+      );
+      final inSecondGroup = await database.playerGroupDao.isPlayerInGroup(
+        playerId: testPlayer1.id,
+        groupId: secondGroup.id,
+      );
+
+      expect(inFirstGroup, true);
+      expect(inSecondGroup, true);
+    });
+
+    // Verifies that removing player from one group doesn't affect other groups.
+    test('Removing player from one group does not affect other groups', () async {
+      final secondGroup = Group(name: 'Second Group', members: [testPlayer1]);
+      await database.groupDao.addGroup(group: testGroup);
+      await database.groupDao.addGroup(group: secondGroup);
+
+      // Remove testPlayer1 from testGroup
+      await database.playerGroupDao.removePlayerFromGroup(
+        playerId: testPlayer1.id,
+        groupId: testGroup.id,
+      );
+
+      final inFirstGroup = await database.playerGroupDao.isPlayerInGroup(
+        playerId: testPlayer1.id,
+        groupId: testGroup.id,
+      );
+      final inSecondGroup = await database.playerGroupDao.isPlayerInGroup(
+        playerId: testPlayer1.id,
+        groupId: secondGroup.id,
+      );
+
+      expect(inFirstGroup, false);
+      expect(inSecondGroup, true);
+    });
+
+    // Verifies that addPlayerToGroup returns true on successful addition.
+    test('addPlayerToGroup returns true on successful addition', () async {
+      await database.groupDao.addGroup(group: testGroup);
+      await database.playerDao.addPlayer(player: testPlayer4);
+
+      final result = await database.playerGroupDao.addPlayerToGroup(
+        player: testPlayer4,
+        groupId: testGroup.id,
+      );
+
+      expect(result, true);
+    });
+
+    // Verifies that removing the same player twice returns false on second attempt.
+    test('Removing same player twice returns false on second attempt', () async {
+      await database.groupDao.addGroup(group: testGroup);
+
+      final firstRemoval = await database.playerGroupDao.removePlayerFromGroup(
+        playerId: testPlayer1.id,
+        groupId: testGroup.id,
+      );
+      expect(firstRemoval, true);
+
+      final secondRemoval = await database.playerGroupDao.removePlayerFromGroup(
+        playerId: testPlayer1.id,
+        groupId: testGroup.id,
+      );
+      expect(secondRemoval, false);
+    });
   });
 }