diff --git a/src/Controller/BlocksController.php b/src/Controller/BlocksController.php
index c5b918c..14f9311 100644
--- a/src/Controller/BlocksController.php
+++ b/src/Controller/BlocksController.php
@@ -40,7 +40,7 @@ private function getEditableConfig() {
   /**
    * Function to export custom blocks.
    */
-  public function exportBlocks(array $form = NULL, FormStateInterface $form_state = NULL) {
+  public function exportBlocks(?array $form = NULL, ?FormStateInterface $form_state = NULL) {
     StructureSyncHelper::logMessage('Custom blocks export started');
 
     if (is_object($form_state) && $form_state->hasValue('export_block_list')) {
@@ -109,7 +109,7 @@ public function exportBlocks(array $form = NULL, FormStateInterface $form_state
    * an array with a key value pair for form with key 'style' and value 'full',
    * 'safe' or 'force' to apply that import style.
    */
-  public function importBlocks(array $form, FormStateInterface $form_state = NULL) {
+  public function importBlocks(array $form, ?FormStateInterface $form_state = NULL) {
     StructureSyncHelper::logMessage('Custom blocks import started');
 
     // Check if the import style has been defined in the form (state) and else
diff --git a/src/Controller/MenuLinksController.php b/src/Controller/MenuLinksController.php
index 95cc029..d512ee3 100644
--- a/src/Controller/MenuLinksController.php
+++ b/src/Controller/MenuLinksController.php
@@ -36,7 +36,7 @@ class MenuLinksController extends ControllerBase {
    * @param \Drupal\Core\Menu\MenuLinkTreeInterface $menuTree
    *   The menu tree service.
    */
-  public function __construct(MenuLinkTreeInterface $menuTree = NULL) {
+  public function __construct(?MenuLinkTreeInterface $menuTree = NULL) {
     $this->config = $this->getEditableConfig();
     $this->entityTypeManager();
 
@@ -66,7 +66,7 @@ private function getEditableConfig() {
   /**
    * Function to export menu links.
    */
-  public function exportMenuLinks(array $form = NULL, FormStateInterface $form_state = NULL) {
+  public function exportMenuLinks(?array $form = NULL, ?FormStateInterface $form_state = NULL) {
     StructureSyncHelper::logMessage('Menu links export started');
 
     if (is_object($form_state) && $form_state->hasValue('export_menu_list')) {
@@ -169,7 +169,7 @@ public function menuTreeFlatten(array $tree) {
    * an array with a key value pair for form with key 'style' and value 'full',
    * 'safe' or 'force' to apply that import style.
    */
-  public function importMenuLinks(array $form, FormStateInterface $form_state = NULL) {
+  public function importMenuLinks(array $form, ?FormStateInterface $form_state = NULL) {
     StructureSyncHelper::logMessage('Menu links import started');
 
     // Check if the there is a selection made in a form for what menus need to
diff --git a/src/Controller/TaxonomiesController.php b/src/Controller/TaxonomiesController.php
index 1121902..0e38f4f 100644
--- a/src/Controller/TaxonomiesController.php
+++ b/src/Controller/TaxonomiesController.php
@@ -40,7 +40,7 @@ private function getEditableConfig() {
   /**
    * Function to export taxonomy terms.
    */
-  public function exportTaxonomies(array $form = NULL, FormStateInterface $form_state = NULL) {
+  public function exportTaxonomies(?array $form = NULL, ?FormStateInterface $form_state = NULL) {
     StructureSyncHelper::logMessage('Taxonomies export started');
 
     if (is_object($form_state) && $form_state->hasValue('export_voc_list')) {
@@ -163,7 +163,7 @@ public function exportTaxonomies(array $form = NULL, FormStateInterface $form_st
    * an array with a key value pair for form with key 'style' and value 'full',
    * 'safe' or 'force' to apply that import style.
    */
-  public function importTaxonomies(array $form, FormStateInterface $form_state = NULL) {
+  public function importTaxonomies(array $form, ?FormStateInterface $form_state = NULL) {
     StructureSyncHelper::logMessage('Taxonomy import started');
 
     // Check if the import style has been defined in the form (state) and else
diff --git a/src/Form/BlocksSyncForm.php b/src/Form/BlocksSyncForm.php
index 747cd73..a1320d2 100644
--- a/src/Form/BlocksSyncForm.php
+++ b/src/Form/BlocksSyncForm.php
@@ -41,7 +41,7 @@ public function getFormId() {
   /**
    * Class constructor.
    */
-  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, Connection $database = NULL, EntityTypeManagerInterface $entityManager = NULL) {
+  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, ?Connection $database = NULL, ?EntityTypeManagerInterface $entityManager = NULL) {
     parent::__construct($config_factory, $typedConfigManager);
 
     if (!\is_null($database)) {
diff --git a/src/Form/MenuSyncForm.php b/src/Form/MenuSyncForm.php
index 1bc8f36..de1a55b 100644
--- a/src/Form/MenuSyncForm.php
+++ b/src/Form/MenuSyncForm.php
@@ -32,7 +32,7 @@ public function getFormId() {
   /**
    * Class constructor.
    */
-  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, Connection $database = NULL) {
+  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, ?Connection $database = NULL) {
     parent::__construct($config_factory, $typedConfigManager);
 
     if (!\is_null($database)) {
diff --git a/src/Form/TaxonomiesSyncForm.php b/src/Form/TaxonomiesSyncForm.php
index fa41d34..de69f1e 100644
--- a/src/Form/TaxonomiesSyncForm.php
+++ b/src/Form/TaxonomiesSyncForm.php
@@ -32,7 +32,7 @@ public function getFormId() {
   /**
    * Class constructor.
    */
-  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, EntityTypeManagerInterface $entityTypeManager = NULL) {
+  public function __construct(ConfigFactoryInterface $config_factory, TypedConfigManagerInterface $typedConfigManager, ?EntityTypeManagerInterface $entityTypeManager = NULL) {
     parent::__construct($config_factory, $typedConfigManager);
 
     if (!\is_null($entityTypeManager)) {
diff --git a/src/StructureSyncHelper.php b/src/StructureSyncHelper.php
index caf2fe2..cab38c5 100644
--- a/src/StructureSyncHelper.php
+++ b/src/StructureSyncHelper.php
@@ -15,7 +15,7 @@ class StructureSyncHelper {
   /**
    * Function to export taxonomy terms.
    */
-  public static function exportTaxonomies(array $form = NULL, FormStateInterface $form_state = NULL) {
+  public static function exportTaxonomies(?array $form = NULL, ?FormStateInterface $form_state = NULL) {
     $taxonomiesController = new TaxonomiesController();
     $taxonomiesController->exportTaxonomies($form, $form_state);
   }
@@ -23,7 +23,7 @@ public static function exportTaxonomies(array $form = NULL, FormStateInterface $
   /**
    * Function to export custom blocks.
    */
-  public static function exportCustomBlocks(array $form = NULL, FormStateInterface $form_state = NULL) {
+  public static function exportCustomBlocks(?array $form = NULL, ?FormStateInterface $form_state = NULL) {
     $blocksController = new BlocksController();
     $blocksController->exportBlocks($form, $form_state);
   }
@@ -31,7 +31,7 @@ public static function exportCustomBlocks(array $form = NULL, FormStateInterface
   /**
    * Function to export menu links.
    */
-  public static function exportMenuLinks(array $form = NULL, FormStateInterface $form_state = NULL) {
+  public static function exportMenuLinks(?array $form = NULL, ?FormStateInterface $form_state = NULL) {
     $menuLinksController = MenuLinksController::create(\Drupal::getContainer());
     $menuLinksController->exportMenuLinks($form, $form_state);
   }
@@ -43,7 +43,7 @@ public static function exportMenuLinks(array $form = NULL, FormStateInterface $f
    * an array with a key value pair for form with key 'style' and value 'full',
    * 'safe' or 'force' to apply that import style.
    */
-  public static function importTaxonomies(array $form, FormStateInterface $form_state = NULL) {
+  public static function importTaxonomies(array $form, ?FormStateInterface $form_state = NULL) {
     $taxonomiesController = new TaxonomiesController();
     $taxonomiesController->importTaxonomies($form, $form_state);
   }
@@ -55,7 +55,7 @@ public static function importTaxonomies(array $form, FormStateInterface $form_st
    * an array with a key value pair for form with key 'style' and value 'full',
    * 'safe' or 'force' to apply that import style.
    */
-  public static function importCustomBlocks(array $form, FormStateInterface $form_state = NULL) {
+  public static function importCustomBlocks(array $form, ?FormStateInterface $form_state = NULL) {
     $customBlocksController = new BlocksController();
     $customBlocksController->importBlocks($form, $form_state);
   }
@@ -67,7 +67,7 @@ public static function importCustomBlocks(array $form, FormStateInterface $form_
    * an array with a key value pair for form with key 'style' and value 'full',
    * 'safe' or 'force' to apply that import style.
    */
-  public static function importMenuLinks(array $form, FormStateInterface $form_state = NULL) {
+  public static function importMenuLinks(array $form, ?FormStateInterface $form_state = NULL) {
     $menuLinksController = MenuLinksController::create(\Drupal::getContainer());
     $menuLinksController->importMenuLinks($form, $form_state);
   }
@@ -100,7 +100,7 @@ public static function logMessage($message, $type = NULL, $context = []) {
   /**
    * Function to start importing taxonomies with the 'full' style.
    */
-  public static function importTaxonomiesFull(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importTaxonomiesFull(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'full';
 
     StructureSyncHelper::importTaxonomies($form, $form_state);
@@ -109,7 +109,7 @@ public static function importTaxonomiesFull(array &$form, FormStateInterface $fo
   /**
    * Function to start importing taxonomies with the 'safe' style.
    */
-  public static function importTaxonomiesSafe(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importTaxonomiesSafe(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'safe';
 
     StructureSyncHelper::importTaxonomies($form, $form_state);
@@ -118,7 +118,7 @@ public static function importTaxonomiesSafe(array &$form, FormStateInterface $fo
   /**
    * Function to start importing taxonomies with the 'force' style.
    */
-  public static function importTaxonomiesForce(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importTaxonomiesForce(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'force';
 
     StructureSyncHelper::importTaxonomies($form, $form_state);
@@ -127,7 +127,7 @@ public static function importTaxonomiesForce(array &$form, FormStateInterface $f
   /**
    * Function to start importing custom blocks with the 'full' style.
    */
-  public static function importCustomBlocksFull(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importCustomBlocksFull(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'full';
 
     StructureSyncHelper::importCustomBlocks($form, $form_state);
@@ -136,7 +136,7 @@ public static function importCustomBlocksFull(array &$form, FormStateInterface $
   /**
    * Function to start importing custom blocks with the 'safe' style.
    */
-  public static function importCustomBlocksSafe(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importCustomBlocksSafe(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'safe';
 
     StructureSyncHelper::importCustomBlocks($form, $form_state);
@@ -145,7 +145,7 @@ public static function importCustomBlocksSafe(array &$form, FormStateInterface $
   /**
    * Function to start importing custom blocks with the 'force' style.
    */
-  public static function importCustomBlocksForce(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importCustomBlocksForce(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'force';
 
     StructureSyncHelper::importCustomBlocks($form, $form_state);
@@ -154,7 +154,7 @@ public static function importCustomBlocksForce(array &$form, FormStateInterface
   /**
    * Function to start importing menu links with the 'full' style.
    */
-  public static function importMenuLinksFull(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importMenuLinksFull(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'full';
 
     StructureSyncHelper::importMenuLinks($form, $form_state);
@@ -163,7 +163,7 @@ public static function importMenuLinksFull(array &$form, FormStateInterface $for
   /**
    * Function to start importing menu links with the 'safe' style.
    */
-  public static function importMenuLinksSafe(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importMenuLinksSafe(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'safe';
 
     StructureSyncHelper::importMenuLinks($form, $form_state);
@@ -172,7 +172,7 @@ public static function importMenuLinksSafe(array &$form, FormStateInterface $for
   /**
    * Function to start importing menu links with the 'force' style.
    */
-  public static function importMenuLinksForce(array &$form, FormStateInterface $form_state = NULL) {
+  public static function importMenuLinksForce(array &$form, ?FormStateInterface $form_state = NULL) {
     $form['style'] = 'force';
 
     StructureSyncHelper::importMenuLinks($form, $form_state);
diff --git a/structure_sync.info.yml b/structure_sync.info.yml
index 7776f05..33b10c6 100644
--- a/structure_sync.info.yml
+++ b/structure_sync.info.yml
@@ -1,6 +1,6 @@
 name: 'Structure Sync'
 description: 'Tool for syncing structural data that is stored as content.'
-core_version_requirement: ^8 || ^9 || ^10 || ^11
+core_version_requirement: ^10.1 || ^11 || ^12
 configure: structure_sync.general.form
 dependencies:
   - drupal:taxonomy
diff --git a/tests/src/Functional/StructureSyncBlocksDrushTest.php b/tests/src/Functional/StructureSyncBlocksDrushTest.php
index 5a97449..6537f11 100644
--- a/tests/src/Functional/StructureSyncBlocksDrushTest.php
+++ b/tests/src/Functional/StructureSyncBlocksDrushTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\structure_sync\Functional;
 
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
 use Drupal\block_content\Entity\BlockContent;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\Tests\structure_sync\Traits\StructureSyncBlocksSetUpTrait;
@@ -12,6 +14,8 @@
  *
  * @group structure_sync
  */
+#[Group('structure_sync')]
+#[RunTestsInSeparateProcesses]
 class StructureSyncBlocksDrushTest extends BrowserTestBase {
 
   use DrushTestTrait;
diff --git a/tests/src/Functional/StructureSyncMenuLinksDrushTest.php b/tests/src/Functional/StructureSyncMenuLinksDrushTest.php
index 6401423..8b98582 100644
--- a/tests/src/Functional/StructureSyncMenuLinksDrushTest.php
+++ b/tests/src/Functional/StructureSyncMenuLinksDrushTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\structure_sync\Functional;
 
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
 use Drupal\menu_link_content\Entity\MenuLinkContent;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\Tests\structure_sync\Traits\StructureSyncMenuLinksSetUpTrait;
@@ -12,6 +14,8 @@
  *
  * @group structure_sync
  */
+#[Group('structure_sync')]
+#[RunTestsInSeparateProcesses]
 class StructureSyncMenuLinksDrushTest extends BrowserTestBase {
 
   use DrushTestTrait;
diff --git a/tests/src/Functional/StructureSyncTaxonomiesDrushTest.php b/tests/src/Functional/StructureSyncTaxonomiesDrushTest.php
index 46ae376..634464b 100644
--- a/tests/src/Functional/StructureSyncTaxonomiesDrushTest.php
+++ b/tests/src/Functional/StructureSyncTaxonomiesDrushTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\structure_sync\Functional;
 
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
 use Drupal\taxonomy\Entity\Term;
 use Drupal\Tests\BrowserTestBase;
 use Drupal\Tests\structure_sync\Traits\StructureSyncTaxonomiesSetUpTrait;
@@ -12,6 +14,8 @@
  *
  * @group structure_sync
  */
+#[Group('structure_sync')]
+#[RunTestsInSeparateProcesses]
 class StructureSyncTaxonomiesDrushTest extends BrowserTestBase {
 
   use DrushTestTrait;
diff --git a/tests/src/FunctionalJavascript/StructureSyncBlocksTest.php b/tests/src/FunctionalJavascript/StructureSyncBlocksTest.php
index 290c915..309933e 100644
--- a/tests/src/FunctionalJavascript/StructureSyncBlocksTest.php
+++ b/tests/src/FunctionalJavascript/StructureSyncBlocksTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\structure_sync\FunctionalJavascript;
 
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
 use Drupal\block_content\Entity\BlockContent;
 use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
 use Drupal\Tests\structure_sync\Traits\StructureSyncBlocksSetUpTrait;
@@ -11,6 +13,8 @@
  *
  * @group structure_sync
  */
+#[Group('structure_sync')]
+#[RunTestsInSeparateProcesses]
 class StructureSyncBlocksTest extends WebDriverTestBase {
 
   use StructureSyncBlocksSetUpTrait;
diff --git a/tests/src/FunctionalJavascript/StructureSyncMenuLinksTest.php b/tests/src/FunctionalJavascript/StructureSyncMenuLinksTest.php
index 060dd7b..8159d03 100644
--- a/tests/src/FunctionalJavascript/StructureSyncMenuLinksTest.php
+++ b/tests/src/FunctionalJavascript/StructureSyncMenuLinksTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\structure_sync\FunctionalJavascript;
 
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
 use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
 use Drupal\menu_link_content\Entity\MenuLinkContent;
 use Drupal\Tests\structure_sync\Traits\StructureSyncMenuLinksSetUpTrait;
@@ -11,6 +13,8 @@
  *
  * @group structure_sync
  */
+#[Group('structure_sync')]
+#[RunTestsInSeparateProcesses]
 class StructureSyncMenuLinksTest extends WebDriverTestBase {
 
   use StructureSyncMenuLinksSetUpTrait;
diff --git a/tests/src/FunctionalJavascript/StructureSyncTaxonomiesTest.php b/tests/src/FunctionalJavascript/StructureSyncTaxonomiesTest.php
index 3881747..9066d32 100644
--- a/tests/src/FunctionalJavascript/StructureSyncTaxonomiesTest.php
+++ b/tests/src/FunctionalJavascript/StructureSyncTaxonomiesTest.php
@@ -2,6 +2,8 @@
 
 namespace Drupal\Tests\structure_sync\FunctionalJavascript;
 
+use PHPUnit\Framework\Attributes\Group;
+use PHPUnit\Framework\Attributes\RunTestsInSeparateProcesses;
 use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
 use Drupal\taxonomy\Entity\Term;
 use Drupal\Tests\structure_sync\Traits\StructureSyncTaxonomiesSetUpTrait;
@@ -11,6 +13,8 @@
  *
  * @group structure_sync
  */
+#[Group('structure_sync')]
+#[RunTestsInSeparateProcesses]
 class StructureSyncTaxonomiesTest extends WebDriverTestBase {
 
   use StructureSyncTaxonomiesSetUpTrait;