diff --git a/apps/dav/tests/unit/CalDAV/Reminder/BackendTest.php b/apps/dav/tests/unit/CalDAV/Reminder/BackendTest.php
index f29b88c5085da..21c949bf56d18 100644
--- a/apps/dav/tests/unit/CalDAV/Reminder/BackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/Reminder/BackendTest.php
@@ -11,9 +11,13 @@
 
 use OCA\DAV\CalDAV\Reminder\Backend as ReminderBackend;
 use OCP\AppFramework\Utility\ITimeFactory;
+use OCP\IDBConnection;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\MockObject\MockObject;
 use Test\TestCase;
 
+#[Group('DB')]
 class BackendTest extends TestCase {
 	private ReminderBackend $reminderBackend;
 	private ITimeFactory&MockObject $timeFactory;
@@ -21,19 +25,19 @@ class BackendTest extends TestCase {
 	protected function setUp(): void {
 		parent::setUp();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->delete('calendar_reminders')->executeStatement();
 		$query->delete('calendarobjects')->executeStatement();
 		$query->delete('calendars')->executeStatement();
 
 		$this->timeFactory = $this->createMock(ITimeFactory::class);
-		$this->reminderBackend = new ReminderBackend(self::$realDatabase, $this->timeFactory);
+		$this->reminderBackend = new ReminderBackend(Server::get(IDBConnection::class), $this->timeFactory);
 
 		$this->createRemindersTestSet();
 	}
 
 	protected function tearDown(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->delete('calendar_reminders')->executeStatement();
 		$query->delete('calendarobjects')->executeStatement();
 		$query->delete('calendars')->executeStatement();
@@ -42,7 +46,7 @@ protected function tearDown(): void {
 	}
 
 	public function testCleanRemindersForEvent(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -52,7 +56,7 @@ public function testCleanRemindersForEvent(): void {
 
 		$this->reminderBackend->cleanRemindersForEvent(1);
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -62,7 +66,7 @@ public function testCleanRemindersForEvent(): void {
 	}
 
 	public function testCleanRemindersForCalendar(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -72,7 +76,7 @@ public function testCleanRemindersForCalendar(): void {
 
 		$this->reminderBackend->cleanRemindersForCalendar(1);
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -82,7 +86,7 @@ public function testCleanRemindersForCalendar(): void {
 	}
 
 	public function testRemoveReminder(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -92,7 +96,7 @@ public function testRemoveReminder(): void {
 
 		$this->reminderBackend->removeReminder((int)$rows[3]['id']);
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -189,7 +193,7 @@ public function testGetAllScheduledRemindersForEvent(): void {
 	}
 
 	public function testInsertReminder(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -200,7 +204,7 @@ public function testInsertReminder(): void {
 		$this->reminderBackend->insertReminder(42, 1337, 'uid99', true, 12345678,
 			true, 'hash99', 'hash42', 'AUDIO', false, 12345670, false);
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -227,7 +231,7 @@ public function testInsertReminder(): void {
 	}
 
 	public function testUpdateReminder(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$rows = $query->select('*')
 			->from('calendar_reminders')
 			->executeQuery()
@@ -242,7 +246,7 @@ public function testUpdateReminder(): void {
 
 		$this->reminderBackend->updateReminder($reminderId, $newNotificationDate);
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$row = $query->select('notification_date')
 			->from('calendar_reminders')
 			->where($query->expr()->eq('id', $query->createNamedParameter($reminderId)))
@@ -253,7 +257,7 @@ public function testUpdateReminder(): void {
 	}
 
 	private function createRemindersTestSet(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendars')
 			->values([
 				'id' => $query->createNamedParameter(1),
@@ -262,7 +266,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendars')
 			->values([
 				'id' => $query->createNamedParameter(99),
@@ -271,7 +275,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendarobjects')
 			->values([
 				'id' => $query->createNamedParameter(1),
@@ -281,7 +285,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendarobjects')
 			->values([
 				'id' => $query->createNamedParameter(2),
@@ -291,7 +295,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendarobjects')
 			->values([
 				'id' => $query->createNamedParameter(10),
@@ -301,7 +305,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendar_reminders')
 			->values([
 				'calendar_id' => $query->createNamedParameter(1),
@@ -319,7 +323,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendar_reminders')
 			->values([
 				'calendar_id' => $query->createNamedParameter(1),
@@ -337,7 +341,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendar_reminders')
 			->values([
 				'calendar_id' => $query->createNamedParameter(1),
@@ -355,7 +359,7 @@ private function createRemindersTestSet(): void {
 			])
 			->executeStatement();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendar_reminders')
 			->values([
 				'calendar_id' => $query->createNamedParameter(99),
diff --git a/apps/dav/tests/unit/CalDAV/ResourceBooking/AbstractPrincipalBackendTestCase.php b/apps/dav/tests/unit/CalDAV/ResourceBooking/AbstractPrincipalBackendTestCase.php
index d13443c8c66e8..a1a185a07fbba 100644
--- a/apps/dav/tests/unit/CalDAV/ResourceBooking/AbstractPrincipalBackendTestCase.php
+++ b/apps/dav/tests/unit/CalDAV/ResourceBooking/AbstractPrincipalBackendTestCase.php
@@ -12,9 +12,11 @@
 use OCA\DAV\CalDAV\Proxy\ProxyMapper;
 use OCA\DAV\CalDAV\ResourceBooking\ResourcePrincipalBackend;
 use OCA\DAV\CalDAV\ResourceBooking\RoomPrincipalBackend;
+use OCP\IDBConnection;
 use OCP\IGroupManager;
 use OCP\IUser;
 use OCP\IUserSession;
+use OCP\Server;
 use PHPUnit\Framework\MockObject\MockObject;
 use Psr\Log\LoggerInterface;
 use Sabre\DAV\PropPatch;
@@ -42,7 +44,7 @@ protected function setUp(): void {
 	}
 
 	protected function tearDown(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 
 		$query->delete('calendar_resources')->executeStatement();
 		$query->delete('calendar_resources_md')->executeStatement();
@@ -52,8 +54,7 @@ protected function tearDown(): void {
 
 	public function testGetPrincipalsByPrefix(): void {
 		$actual = $this->principalBackend->getPrincipalsByPrefix($this->principalPrefix);
-
-		$this->assertEquals([
+		$this->assertEqualsCanonicalizing([
 			[
 				'uri' => $this->principalPrefix . '/backend1-res1',
 				'{DAV:}displayname' => 'Beamer1',
@@ -264,7 +265,8 @@ public function testSearchPrincipals($expected, $test): void {
 			'{DAV:}displayname' => 'Beamer',
 		], $test);
 
-		$this->assertEquals(
+		// The query has no ORDER BY, so result order is not guaranteed by the DB
+		$this->assertEqualsCanonicalizing(
 			str_replace('%prefix%', $this->principalPrefix, $expected),
 			$actual);
 	}
@@ -454,7 +456,7 @@ public function testFindByUriByUnknownUri(): void {
 	}
 
 	protected function createTestDatasetInDb() {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert($this->mainDbTable)
 			->values([
 				'backend_id' => $query->createNamedParameter('backend1'),
diff --git a/apps/dav/tests/unit/CalDAV/ResourceBooking/ResourcePrincipalBackendTest.php b/apps/dav/tests/unit/CalDAV/ResourceBooking/ResourcePrincipalBackendTest.php
index 1e3068cdfc4f1..3824b711d7ad5 100644
--- a/apps/dav/tests/unit/CalDAV/ResourceBooking/ResourcePrincipalBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/ResourceBooking/ResourcePrincipalBackendTest.php
@@ -9,12 +9,16 @@
 namespace OCA\DAV\Tests\unit\CalDAV\ResourceBooking;
 
 use OCA\DAV\CalDAV\ResourceBooking\ResourcePrincipalBackend;
+use OCP\IDBConnection;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\Group;
 
+#[Group('DB')]
 class ResourcePrincipalBackendTest extends AbstractPrincipalBackendTestCase {
 	protected function setUp(): void {
 		parent::setUp();
 
-		$this->principalBackend = new ResourcePrincipalBackend(self::$realDatabase,
+		$this->principalBackend = new ResourcePrincipalBackend(Server::get(IDBConnection::class),
 			$this->userSession, $this->groupManager, $this->logger, $this->proxyMapper);
 
 		$this->mainDbTable = 'calendar_resources';
diff --git a/apps/dav/tests/unit/CalDAV/ResourceBooking/RoomPrincipalBackendTest.php b/apps/dav/tests/unit/CalDAV/ResourceBooking/RoomPrincipalBackendTest.php
index 845ff74dc1016..4cbc88f6ace0d 100644
--- a/apps/dav/tests/unit/CalDAV/ResourceBooking/RoomPrincipalBackendTest.php
+++ b/apps/dav/tests/unit/CalDAV/ResourceBooking/RoomPrincipalBackendTest.php
@@ -9,12 +9,16 @@
 namespace OCA\DAV\Tests\unit\CalDAV\ResourceBooking;
 
 use OCA\DAV\CalDAV\ResourceBooking\RoomPrincipalBackend;
+use OCP\IDBConnection;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\Group;
 
+#[Group('DB')]
 class RoomPrincipalBackendTest extends AbstractPrincipalBackendTestCase {
 	protected function setUp(): void {
 		parent::setUp();
 
-		$this->principalBackend = new RoomPrincipalBackend(self::$realDatabase,
+		$this->principalBackend = new RoomPrincipalBackend(Server::get(IDBConnection::class),
 			$this->userSession, $this->groupManager, $this->logger, $this->proxyMapper);
 
 		$this->mainDbTable = 'calendar_rooms';
diff --git a/apps/user_status/tests/Unit/Db/UserStatusMapperTest.php b/apps/user_status/tests/Unit/Db/UserStatusMapperTest.php
index f6f924b91fdf3..e59df1fa0f4ed 100644
--- a/apps/user_status/tests/Unit/Db/UserStatusMapperTest.php
+++ b/apps/user_status/tests/Unit/Db/UserStatusMapperTest.php
@@ -13,8 +13,12 @@
 use OCA\UserStatus\Db\UserStatusMapper;
 use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\DB\Exception;
+use OCP\IDBConnection;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\Group;
 use Test\TestCase;
 
+#[Group('DB')]
 class UserStatusMapperTest extends TestCase {
 	private UserStatusMapper $mapper;
 
@@ -22,10 +26,10 @@ protected function setUp(): void {
 		parent::setUp();
 
 		// make sure that DB is empty
-		$qb = self::$realDatabase->getQueryBuilder();
+		$qb = Server::get(IDBConnection::class)->getQueryBuilder();
 		$qb->delete('user_status')->executeStatement();
 
-		$this->mapper = new UserStatusMapper(self::$realDatabase);
+		$this->mapper = new UserStatusMapper(Server::get(IDBConnection::class));
 	}
 
 	public function testGetTableName(): void {
diff --git a/tests/lib/Calendar/ResourcesRoomsUpdaterTest.php b/tests/lib/Calendar/ResourcesRoomsUpdaterTest.php
index e74ba90c96532..9a85264cca2bd 100644
--- a/tests/lib/Calendar/ResourcesRoomsUpdaterTest.php
+++ b/tests/lib/Calendar/ResourcesRoomsUpdaterTest.php
@@ -17,6 +17,9 @@
 use OCP\Calendar\Resource\IManager as IResourceManager;
 use OCP\Calendar\Resource\IResource;
 use OCP\Calendar\Room\IManager as IRoomManager;
+use OCP\IDBConnection;
+use OCP\Server;
+use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\MockObject\MockObject;
 use Psr\Container\ContainerInterface;
 use Test\TestCase;
@@ -24,6 +27,7 @@
 interface tmpI extends IResource, IMetadataProvider {
 }
 
+#[Group('DB')]
 class ResourcesRoomsUpdaterTest extends TestCase {
 	private ResourcesRoomsUpdater $updater;
 
@@ -56,14 +60,14 @@ protected function setUp(): void {
 
 		$this->updater = new ResourcesRoomsUpdater(
 			$this->container,
-			self::$realDatabase,
+			Server::get(IDBConnection::class),
 			$this->calDavBackend
 		);
 	}
 
 	#[\Override]
 	protected function tearDown(): void {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->delete('calendar_resources')->executeStatement();
 		$query->delete('calendar_resources_md')->executeStatement();
 		$query->delete('calendar_rooms')->executeStatement();
@@ -209,7 +213,7 @@ public function testUpdateBoth(): void {
 		$this->updater->updateResources();
 		$this->updater->updateRooms();
 
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->select('*')->from('calendar_resources');
 
 		$rows = [];
@@ -221,7 +225,7 @@ public function testUpdateBoth(): void {
 			$rows[] = $row;
 		}
 
-		$this->assertEquals([
+		$this->assertEqualsCanonicalizing([
 			[
 				'backend_id' => 'backend1',
 				'resource_id' => 'res1',
@@ -280,7 +284,7 @@ public function testUpdateBoth(): void {
 			],
 		], $rows);
 
-		$query2 = self::$realDatabase->getQueryBuilder();
+		$query2 = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query2->select('*')->from('calendar_resources_md');
 
 		$rows2 = [];
@@ -290,7 +294,7 @@ public function testUpdateBoth(): void {
 			$rows2[] = $row;
 		}
 
-		$this->assertEquals([
+		$this->assertEqualsCanonicalizing([
 			[
 				'resource_id' => $ids['backend2::res3'],
 				'key' => 'meta1',
@@ -335,7 +339,7 @@ public function testUpdateBoth(): void {
 	}
 
 	protected function createTestResourcesInCache() {
-		$query = self::$realDatabase->getQueryBuilder();
+		$query = Server::get(IDBConnection::class)->getQueryBuilder();
 		$query->insert('calendar_resources')
 			->values([
 				'backend_id' => $query->createNamedParameter('backend1'),
diff --git a/tests/lib/TestCase.php b/tests/lib/TestCase.php
index aa091b98113ef..0d54d7c6f64df 100644
--- a/tests/lib/TestCase.php
+++ b/tests/lib/TestCase.php
@@ -43,7 +43,7 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase {
 	private QueueBus $commandBus;
 
 	/** @psalm-suppress ImpureStaticProperty For tests it's not an issue */
-	protected static ?IDBConnection $realDatabase = null;
+	private static ?IDBConnection $realDatabase = null;
 	/** @psalm-suppress ImpureStaticProperty */
 	private static bool $wasDatabaseAllowed = false;
 	protected array $services = [];