diff --git a/.drone.yml b/.drone.yml
index c0b07a7addd..f31bdf67d39 100644
--- a/.drone.yml
+++ b/.drone.yml
@@ -29,7 +29,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -64,7 +64,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -99,7 +99,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -136,7 +136,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -173,7 +173,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -208,7 +208,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -243,7 +243,7 @@ trigger:
     - master
     - stable*
   event:
-    - pull_request
+#    - pull_request
     - push
 
 ---
@@ -279,7 +279,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -288,7 +292,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
@@ -324,7 +328,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -333,7 +341,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
@@ -369,7 +377,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -378,7 +390,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
@@ -416,7 +428,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -425,7 +441,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
@@ -463,7 +479,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -472,7 +492,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
@@ -508,7 +528,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -517,7 +541,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
@@ -553,7 +577,11 @@ services:
       MYSQL_USER: oc_autotest
       MYSQL_PASSWORD: owncloud
       MYSQL_DATABASE: oc_autotest
-    command: [ "--innodb_large_prefix=true", "--innodb_file_format=barracuda", "--innodb_file_per_table=true" ]
+    command:
+      - --innodb_large_prefix=true
+      - --innodb_file_format=barracuda
+      - --innodb_file_per_table=true
+      - --sql-mode=ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION
     tmpfs:
       - /var/lib/mysql
 
@@ -562,7 +590,7 @@ trigger:
     - master
     - stable*
   event:
-#    - pull_request
+    - pull_request
     - push
 
 ---
diff --git a/.github/workflows/phpunit.yml b/.github/workflows/phpunit.yml
index 731b3471fdb..6c92da58247 100644
--- a/.github/workflows/phpunit.yml
+++ b/.github/workflows/phpunit.yml
@@ -103,6 +103,11 @@ jobs:
         options: --health-cmd="mysqladmin ping" --health-interval 5s --health-timeout 2s --health-retries 5
 
     steps:
+      - name: Enable ONLY_FULL_GROUP_BY MySQL option
+        run: |
+          echo "SET GLOBAL sql_mode=(SELECT CONCAT(@@sql_mode,',ONLY_FULL_GROUP_BY'));" | mysql -h 127.0.0.1 -P 4444 -u root -prootpassword
+          echo "SELECT @@sql_mode;" | mysql -h 127.0.0.1 -P 4444 -u root -prootpassword
+
       - name: Checkout server
         uses: actions/checkout@v2
         with:
diff --git a/lib/Chat/MessageParser.php b/lib/Chat/MessageParser.php
index db142107eec..5e8ae8463a1 100644
--- a/lib/Chat/MessageParser.php
+++ b/lib/Chat/MessageParser.php
@@ -92,7 +92,7 @@ protected function setActor(Message $message): void {
 				$displayName = $this->guestNames[$comment->getActorId()];
 			} else {
 				try {
-					$participant = $message->getRoom()->getParticipantByActor(Attendee::ACTOR_GUESTS, $comment->getActorId(), false);
+					$participant = $message->getRoom()->getParticipantByActor(Attendee::ACTOR_GUESTS, $comment->getActorId());
 					$displayName = $participant->getAttendee()->getDisplayName();
 				} catch (ParticipantNotFoundException $e) {
 				}
diff --git a/lib/Chat/Parser/SystemMessage.php b/lib/Chat/Parser/SystemMessage.php
index c29da342167..40db1ae235c 100644
--- a/lib/Chat/Parser/SystemMessage.php
+++ b/lib/Chat/Parser/SystemMessage.php
@@ -695,7 +695,7 @@ protected function getGuest(Room $room, string $actorId): array {
 
 	protected function getGuestName(Room $room, string $actorId): string {
 		try {
-			$participant = $room->getParticipantByActor(Attendee::ACTOR_GUESTS, $actorId, false);
+			$participant = $room->getParticipantByActor(Attendee::ACTOR_GUESTS, $actorId);
 			$name = $participant->getAttendee()->getDisplayName();
 			if ($name === '') {
 				return $this->l->t('Guest');
diff --git a/lib/Chat/Parser/UserMention.php b/lib/Chat/Parser/UserMention.php
index 743fb2caa35..b4bec33c718 100644
--- a/lib/Chat/Parser/UserMention.php
+++ b/lib/Chat/Parser/UserMention.php
@@ -132,7 +132,7 @@ public function parseMessage(Message $chatMessage): void {
 				];
 			} elseif ($mention['type'] === 'guest') {
 				try {
-					$participant = $chatMessage->getRoom()->getParticipantByActor(Attendee::ACTOR_GUESTS, substr($mention['id'], strlen('guest/')), false);
+					$participant = $chatMessage->getRoom()->getParticipantByActor(Attendee::ACTOR_GUESTS, substr($mention['id'], strlen('guest/')));
 					$displayName = $participant->getAttendee()->getDisplayName() ?: $this->l->t('Guest');
 				} catch (ParticipantNotFoundException $e) {
 					$displayName = $this->l->t('Guest');
diff --git a/lib/Controller/RoomController.php b/lib/Controller/RoomController.php
index 57cb0c096ca..18c62d90e23 100644
--- a/lib/Controller/RoomController.php
+++ b/lib/Controller/RoomController.php
@@ -1508,15 +1508,8 @@ protected function changeParticipantType(int $attendeeId,  bool $promote): DataR
 		}
 
 		// Prevent users/moderators modifying themselves
-		if ($attendee->getActorType() === Attendee::ACTOR_USERS) {
-			if ($attendee->getActorId() === $this->userId) {
-				return new DataResponse([], Http::STATUS_FORBIDDEN);
-			}
-		} elseif ($attendee->getActorType() === Attendee::ACTOR_GUESTS) {
-			$session = $targetParticipant->getSession();
-			$currentSessionId = $this->session->getSessionForRoom($this->room->getToken());
-
-			if ($session instanceof Session && $currentSessionId === $session->getSessionId()) {
+		if ($attendee->getActorType() === $this->participant->getAttendee()->getActorType()) {
+			if ($attendee->getActorId() === $this->participant->getAttendee()->getActorId()) {
 				return new DataResponse([], Http::STATUS_FORBIDDEN);
 			}
 		} elseif ($attendee->getActorType() === Attendee::ACTOR_GROUPS) {
diff --git a/lib/Controller/SignalingController.php b/lib/Controller/SignalingController.php
index 962cc087a75..9c7e0a0e309 100644
--- a/lib/Controller/SignalingController.php
+++ b/lib/Controller/SignalingController.php
@@ -601,14 +601,14 @@ private function backendRoom(array $roomRequest): DataResponse {
 						// If the user joins the session might not be known to the server yet.
 						// In this case we load by actor information and use the session id as new session.
 						try {
-							$participant = $room->getParticipantByActor($actorType, $actorId, false);
+							$participant = $room->getParticipantByActor($actorType, $actorId);
 						} catch (ParticipantNotFoundException $e) {
 						}
 					}
 				}
 			} else {
 				try {
-					$participant = $room->getParticipantByActor($actorType, $actorId, false);
+					$participant = $room->getParticipantByActor($actorType, $actorId);
 				} catch (ParticipantNotFoundException $e) {
 				}
 			}
diff --git a/lib/Notification/Notifier.php b/lib/Notification/Notifier.php
index e42dcb29fc9..0b0072536ad 100644
--- a/lib/Notification/Notifier.php
+++ b/lib/Notification/Notifier.php
@@ -492,7 +492,7 @@ protected function parseChatMessage(INotification $notification, Room $room, Par
 	 * @throws ParticipantNotFoundException
 	 */
 	protected function getGuestParameter(Room $room, string $actorId): array {
-		$participant = $room->getParticipantByActor(Attendee::ACTOR_GUESTS, $actorId, false);
+		$participant = $room->getParticipantByActor(Attendee::ACTOR_GUESTS, $actorId);
 		$name = $participant->getAttendee()->getDisplayName();
 		if (trim($name) === '') {
 			throw new ParticipantNotFoundException('Empty name');
diff --git a/lib/Room.php b/lib/Room.php
index 647462b402e..830ccd7e4b2 100644
--- a/lib/Room.php
+++ b/lib/Room.php
@@ -559,13 +559,10 @@ public function getParticipantByPin(string $pin): Participant {
 
 	/**
 	 * @param int $attendeeId
-	 * @param string|null|false $sessionId Set to false if you don't want to load a session (and save resources),
-	 *                                     string to try loading a specific session
-	 *                                     null to try loading "any"
 	 * @return Participant
 	 * @throws ParticipantNotFoundException When the pin is not valid (has no participant assigned)
 	 */
-	public function getParticipantByAttendeeId(int $attendeeId, $sessionId = null): Participant {
+	public function getParticipantByAttendeeId(int $attendeeId): Participant {
 		$query = $this->db->getQueryBuilder();
 		$helper = new SelectHelper();
 		$helper->selectAttendeesTable($query);
@@ -574,20 +571,6 @@ public function getParticipantByAttendeeId(int $attendeeId, $sessionId = null):
 			->andWhere($query->expr()->eq('a.room_id', $query->createNamedParameter($this->getId())))
 			->setMaxResults(1);
 
-		if ($sessionId !== false) {
-			if ($sessionId !== null) {
-				$helper->selectSessionsTable($query);
-				$query->leftJoin('a', 'talk_sessions', 's', $query->expr()->andX(
-					$query->expr()->eq('s.session_id', $query->createNamedParameter($sessionId)),
-					$query->expr()->eq('a.id', 's.attendee_id')
-				));
-			} else {
-				$helper->selectSessionsTableMax($query);
-				$query->groupBy('a.id');
-				$query->leftJoin('a', 'talk_sessions', 's', $query->expr()->eq('a.id', 's.attendee_id'));
-			}
-		}
-
 		$result = $query->executeQuery();
 		$row = $result->fetch();
 		$result->closeCursor();
@@ -602,15 +585,12 @@ public function getParticipantByAttendeeId(int $attendeeId, $sessionId = null):
 	/**
 	 * @param string $actorType
 	 * @param string $actorId
-	 * @param string|null|false $sessionId Set to false if you don't want to load a session (and save resources),
-	 *                                     string to try loading a specific session
-	 *                                     null to try loading "any"
 	 * @return Participant
 	 * @throws ParticipantNotFoundException When the pin is not valid (has no participant assigned)
 	 */
-	public function getParticipantByActor(string $actorType, string $actorId, $sessionId = null): Participant {
+	public function getParticipantByActor(string $actorType, string $actorId): Participant {
 		if ($actorType === Attendee::ACTOR_USERS) {
-			return $this->getParticipant($actorId, $sessionId);
+			return $this->getParticipant($actorId, false);
 		}
 
 		$query = $this->db->getQueryBuilder();
@@ -622,20 +602,6 @@ public function getParticipantByActor(string $actorType, string $actorId, $sessi
 			->andWhere($query->expr()->eq('a.room_id', $query->createNamedParameter($this->getId())))
 			->setMaxResults(1);
 
-		if ($sessionId !== false) {
-			if ($sessionId !== null) {
-				$helper->selectSessionsTable($query);
-				$query->leftJoin('a', 'talk_sessions', 's', $query->expr()->andX(
-					$query->expr()->eq('s.session_id', $query->createNamedParameter($sessionId)),
-					$query->expr()->eq('a.id', 's.attendee_id')
-				));
-			} else {
-				$helper->selectSessionsTableMax($query);
-				$query->groupBy('a.id');
-				$query->leftJoin('a', 'talk_sessions', 's', $query->expr()->eq('a.id', 's.attendee_id'));
-			}
-		}
-
 		$result = $query->executeQuery();
 		$row = $result->fetch();
 		$result->closeCursor();
diff --git a/lib/Service/ParticipantService.php b/lib/Service/ParticipantService.php
index 2bd4010fdc1..6dc318ccc8a 100644
--- a/lib/Service/ParticipantService.php
+++ b/lib/Service/ParticipantService.php
@@ -1188,7 +1188,7 @@ public function getParticipantsByNotificationLevel(Room $room, int $notification
 
 		$helper = new SelectHelper();
 		$helper->selectAttendeesTable($query);
-		$helper->selectSessionsTableMax($query);
+		$helper->selectSessionsTable($query);
 		$query->from('talk_attendees', 'a')
 			// Currently we only care if the user has a session at all, so we can select any: #ThisIsFine
 			->leftJoin(
@@ -1196,10 +1196,16 @@ public function getParticipantsByNotificationLevel(Room $room, int $notification
 				$query->expr()->eq('s.attendee_id', 'a.id')
 			)
 			->where($query->expr()->eq('a.room_id', $query->createNamedParameter($room->getId(), IQueryBuilder::PARAM_INT)))
-			->andWhere($query->expr()->eq('a.notification_level', $query->createNamedParameter($notificationLevel, IQueryBuilder::PARAM_INT)))
-			->groupBy('a.id');
+			->andWhere($query->expr()->eq('a.notification_level', $query->createNamedParameter($notificationLevel, IQueryBuilder::PARAM_INT)));
 
-		return $this->getParticipantsFromQuery($query, $room);
+		$participants = $this->getParticipantsFromQuery($query, $room);
+
+		$uniqueAttendees = [];
+		foreach ($participants as $participant) {
+			$uniqueAttendees[$participant->getAttendee()->getId()] = $participant;
+		}
+
+		return array_values($uniqueAttendees);
 	}
 
 	/**
diff --git a/tests/php/Service/ParticipantServiceTest.php b/tests/php/Service/ParticipantServiceTest.php
new file mode 100644
index 00000000000..98f23a10e19
--- /dev/null
+++ b/tests/php/Service/ParticipantServiceTest.php
@@ -0,0 +1,152 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * @copyright Copyright (c) 2022 Joas Schilling <coding@schilljs.com>
+ *
+ * @license GNU AGPL version 3 or any later version
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+namespace OCA\Talk\Tests\php\Service;
+
+use OCA\Talk\Config;
+use OCA\Talk\Federation\Notifications;
+use OCA\Talk\Model\Attendee;
+use OCA\Talk\Model\AttendeeMapper;
+use OCA\Talk\Model\Session;
+use OCA\Talk\Model\SessionMapper;
+use OCA\Talk\Participant;
+use OCA\Talk\Room;
+use OCA\Talk\Service\MembershipService;
+use OCA\Talk\Service\ParticipantService;
+use OCA\Talk\Service\SessionService;
+use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\ICacheFactory;
+use OCP\IConfig;
+use OCP\IGroupManager;
+use OCP\IUserManager;
+use OCP\Security\ISecureRandom;
+use PHPUnit\Framework\MockObject\MockObject;
+use Test\TestCase;
+
+/**
+ * @group DB
+ */
+class ParticipantServiceTest extends TestCase {
+
+	/** @var IConfig|MockObject */
+	protected $serverConfig;
+	/** @var Config|MockObject */
+	protected $talkConfig;
+	/** @var AttendeeMapper */
+	protected $attendeeMapper;
+	/** @var SessionMapper */
+	protected $sessionMapper;
+	/** @var SessionService|MockObject */
+	protected $sessionService;
+	/** @var ISecureRandom|MockObject */
+	protected $secureRandom;
+	/** @var IEventDispatcher|MockObject */
+	protected $dispatcher;
+	/** @var IUserManager|MockObject */
+	protected $userManager;
+	/** @var IGroupManager|MockObject */
+	protected $groupManager;
+	/** @var MembershipService|MockObject */
+	protected $membershipService;
+	/** @var Notifications|MockObject */
+	protected $federationNotifications;
+	/** @var ITimeFactory|MockObject */
+	protected $time;
+	/** @var ICacheFactory|MockObject */
+	protected $cacheFactory;
+	/** @var ParticipantService */
+	private $service;
+
+
+	public function setUp(): void {
+		parent::setUp();
+
+		$this->serverConfig = $this->createMock(IConfig::class);
+		$this->talkConfig = $this->createMock(Config::class);
+		$this->attendeeMapper = new AttendeeMapper(\OC::$server->getDatabaseConnection());
+		$this->sessionMapper = new SessionMapper(\OC::$server->getDatabaseConnection());
+		$this->sessionService = $this->createMock(SessionService::class);
+		$this->secureRandom = $this->createMock(ISecureRandom::class);
+		$this->dispatcher = $this->createMock(IEventDispatcher::class);
+		$this->userManager = $this->createMock(IUserManager::class);
+		$this->groupManager = $this->createMock(IGroupManager::class);
+		$this->membershipService = $this->createMock(MembershipService::class);
+		$this->federationNotifications = $this->createMock(Notifications::class);
+		$this->time = $this->createMock(ITimeFactory::class);
+		$this->cacheFactory = $this->createMock(ICacheFactory::class);
+		$this->service = new ParticipantService(
+			$this->serverConfig,
+			$this->talkConfig,
+			$this->attendeeMapper,
+			$this->sessionMapper,
+			$this->sessionService,
+			$this->secureRandom,
+			\OC::$server->getDatabaseConnection(),
+			$this->dispatcher,
+			$this->userManager,
+			$this->groupManager,
+			$this->membershipService,
+			$this->federationNotifications,
+			$this->time,
+			$this->cacheFactory
+		);
+	}
+
+	public function tearDown(): void {
+		try {
+			$attendee = $this->attendeeMapper->findByActor(123456789, Attendee::ACTOR_USERS, 'test');
+			$this->sessionMapper->deleteByAttendeeId($attendee->getId());
+			$this->attendeeMapper->delete($attendee);
+		} catch (DoesNotExistException $exception) {
+		}
+
+		parent::tearDown();
+	}
+
+	public function testGetParticipantsByNotificationLevel(): void {
+		$attendee = new Attendee();
+		$attendee->setActorType(Attendee::ACTOR_USERS);
+		$attendee->setActorId('test');
+		$attendee->setRoomId(123456789);
+		$attendee->setNotificationLevel(Participant::NOTIFY_MENTION);
+		$this->attendeeMapper->insert($attendee);
+
+		$session1 = new Session();
+		$session1->setAttendeeId($attendee->getId());
+		$session1->setSessionId(self::getUniqueID('session1'));
+		$this->sessionMapper->insert($session1);
+
+		$session2 = new Session();
+		$session2->setAttendeeId($attendee->getId());
+		$session2->setSessionId(self::getUniqueID('session2'));
+		$this->sessionMapper->insert($session2);
+
+		$room = $this->createMock(Room::class);
+		$room->method('getId')
+			->willReturn(123456789);
+		$participants = $this->service->getParticipantsByNotificationLevel($room, Participant::NOTIFY_MENTION);
+		self::assertCount(1, $participants);
+	}
+}