diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index c8c597c01d..a47b67baad 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -543,9 +543,7 @@ jobs:
                   New-WebHandler -Name "PHP-FastCGI" -Path "*.php" -Modules FastCgiModule -ScriptProcessor "C:\tools\php\php-cgi.exe" -Verb '*' -ResourceType Either
                   iisreset
                   NET START W3SVC
-                  mkdir "${env:GITHUB_WORKSPACE}\phpBB\cache\test"
-                  mkdir "${env:GITHUB_WORKSPACE}\phpBB\cache\installer"
-                  icacls "${env:GITHUB_WORKSPACE}\phpBB\cache" /grant Users:F /T
+                  icacls "${env:GITHUB_WORKSPACE}\phpBB\cache" /grant "Users:(OI)(CI)F" /T
                   icacls "${env:GITHUB_WORKSPACE}\phpBB\files" /grant Users:F /T
                   icacls "${env:GITHUB_WORKSPACE}\phpBB\store" /grant Users:F /T
                   icacls "${env:GITHUB_WORKSPACE}\phpBB\images\avatars\upload" /grant Users:F /T
diff --git a/tests/functional/extension_controller_test.php b/tests/functional/extension_controller_test.php
index da1a6e18ae..0b95b916ad 100644
--- a/tests/functional/extension_controller_test.php
+++ b/tests/functional/extension_controller_test.php
@@ -55,6 +55,13 @@ class phpbb_functional_extension_controller_test extends phpbb_functional_test_c
 		$this->purge_cache();
 	}
 
+	protected function tearDown(): void
+	{
+		$this->purge_cache();
+
+		parent::tearDown();
+	}
+
 	/**
 	* Check a controller for extension foo/bar.
 	*/
diff --git a/tests/functional/extension_global_lang_test.php b/tests/functional/extension_global_lang_test.php
index 8c9c38937b..ae254b3d84 100644
--- a/tests/functional/extension_global_lang_test.php
+++ b/tests/functional/extension_global_lang_test.php
@@ -54,9 +54,9 @@ class phpbb_functional_extension_global_lang_test extends phpbb_functional_test_
 
 	protected function tearDown(): void
 	{
-		parent::tearDown();
-
 		$this->purge_cache();
+
+		parent::tearDown();
 	}
 
 	public function test_load_extension_lang_globally()
@@ -71,5 +71,7 @@ class phpbb_functional_extension_global_lang_test extends phpbb_functional_test_
 
 		// language from ext/foo/bar/language/en/foo_global.php
 		$this->assertStringContainsString('Overwritten by foo', $crawler->filter('.skiplink')->text());
+
+		$this->phpbb_extension_manager->purge('foo/bar');
 	}
 }
diff --git a/tests/functional/extension_module_test.php b/tests/functional/extension_module_test.php
index 8c676361e6..92e116460a 100644
--- a/tests/functional/extension_module_test.php
+++ b/tests/functional/extension_module_test.php
@@ -40,6 +40,14 @@ class phpbb_functional_extension_module_test extends phpbb_functional_test_case
 		self::$helper->restore_original_ext_dir();
 	}
 
+	protected function tearDown(): void
+	{
+		$this->phpbb_extension_manager->purge('foo/bar');
+		$this->purge_cache();
+
+		parent::tearDown();
+	}
+
 	protected function setUp(): void
 	{
 		global $db;
@@ -131,7 +139,5 @@ class phpbb_functional_extension_module_test extends phpbb_functional_test_case
 		$link = $crawler->selectLink('UCP_FOOBAR_TITLE')->link()->getUri();
 		$crawler = self::request('GET', substr($link, strpos($link, 'ucp.')));
 		$this->assertStringContainsString('UCP Extension Template Test Passed!', $crawler->filter('#content')->text());
-
-		$this->phpbb_extension_manager->purge('foo/bar');
 	}
 }
diff --git a/tests/functional/extension_permission_lang_test.php b/tests/functional/extension_permission_lang_test.php
index 47adc3f87e..3aae7685d8 100644
--- a/tests/functional/extension_permission_lang_test.php
+++ b/tests/functional/extension_permission_lang_test.php
@@ -41,6 +41,13 @@ class phpbb_functional_extension_permission_lang_test extends phpbb_functional_t
 		self::$helper->restore_original_ext_dir();
 	}
 
+	protected function tearDown(): void
+	{
+		$this->purge_cache();
+
+		parent::tearDown();
+	}
+
 	protected function setUp(): void
 	{
 		parent::setUp();
@@ -82,5 +89,7 @@ class phpbb_functional_extension_permission_lang_test extends phpbb_functional_t
 
 		// language from ext/foo/bar/language/en/permissions_foo.php
 		$this->assertStringContainsString('Can view foobar', $crawler->filter('body')->text());
+
+		$this->phpbb_extension_manager->purge('foo/bar');
 	}
 }
diff --git a/tests/functional/extension_template_event_order_test.php b/tests/functional/extension_template_event_order_test.php
index c931c95bc1..c77cb7b89f 100644
--- a/tests/functional/extension_template_event_order_test.php
+++ b/tests/functional/extension_template_event_order_test.php
@@ -39,6 +39,13 @@ class phpbb_functional_extension_template_event_order_test extends phpbb_functio
 		self::$helper->restore_original_ext_dir();
 	}
 
+	protected function tearDown(): void
+	{
+		$this->purge_cache();
+
+		parent::tearDown();
+	}
+
 	protected function setUp(): void
 	{
 		parent::setUp();
diff --git a/tests/functional/metadata_manager_test.php b/tests/functional/metadata_manager_test.php
index 5ef67836c9..5dff5d6227 100644
--- a/tests/functional/metadata_manager_test.php
+++ b/tests/functional/metadata_manager_test.php
@@ -26,6 +26,7 @@ class phpbb_functional_metadata_manager_test extends phpbb_functional_test_case
 
 	protected function tearDown(): void
 	{
+		$this->phpbb_extension_manager->purge('foo/bar');
 		$this->purge_cache();
 
 		parent::tearDown();
diff --git a/tests/test_framework/phpbb_functional_test_case.php b/tests/test_framework/phpbb_functional_test_case.php
index a90008c22e..90cbb40626 100644
--- a/tests/test_framework/phpbb_functional_test_case.php
+++ b/tests/test_framework/phpbb_functional_test_case.php
@@ -980,7 +980,7 @@ class phpbb_functional_test_case extends phpbb_test_case
 		// Any output before the doc type means there was an error
 		$content = self::get_content();
 		self::assertStringNotContainsString('[phpBB Debug]', $content);
-		self::assertStringStartsWith('<!DOCTYPE', strtoupper(substr(trim($content), 0, 10)), 'Output found before DOCTYPE specification.');
+		self::assertStringStartsWith('<!DOCTYPE', strtoupper(substr(trim($content), 0, 10000)), 'Output found before DOCTYPE specification.');
 
 		if ($status_code !== false)
 		{