Fix tests

- Fix InstallerTest case
- Fix native function mocking
- Add returntype for Unit-Tests
- Fixing ExtendedPDO test troubles
- Fix wrong class inheritance path for DatabaseTestTrait.php
- Fix SyslogLogger Server Exception for PHP8
- Add user/contact to database.fixture.php
- Avoid invalid rollbacks for test setup in PHP8

tests/src/Core/Cache/DatabaseCacheTest.php

@@ -36,10 +36,12 @@ class DatabaseCacheTest extends CacheTest
 	use DatabaseTestTrait;
 	use VFSTrait;
 
-	protected function setUp()
+	protected function setUp(): void
 	{
 		$this->setUpVfsDir();
 
+		$this->setUpDb();
+
 		parent::setUp();
 	}
 
@@ -60,9 +62,12 @@ class DatabaseCacheTest extends CacheTest
 		return $this->cache;
 	}
 
-	protected function tearDown()
+	protected function tearDown(): void
 	{
 		$this->cache->clear(false);
+
+		$this->tearDownDb();
+
 		parent::tearDown();
 	}
 }