diff --git a/tests/external/get_preview_test.php b/tests/external/get_preview_test.php
index 1b8e90b..0df9091 100644
--- a/tests/external/get_preview_test.php
+++ b/tests/external/get_preview_test.php
@@ -24,14 +24,14 @@
  * @copyright   2016 David Mudrak <david@moodle.com>
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class get_preview_test extends \advanced_testcase {
+final class get_preview_test extends \advanced_testcase {
 
     /**
      * Test the editor_marklar_get_preview() external function.
      *
      * @runInSeparateProcess
      */
-    public function test_get_preview() {
+    public function test_get_preview(): void {
         global $CFG;
         require_once($CFG->libdir.'/externallib.php');
 
@@ -55,7 +55,7 @@ public function test_get_preview() {
      *
      * @runInSeparateProcess
      */
-    public function test_embeded_images_preview() {
+    public function test_embeded_images_preview(): void {
         global $CFG;
         require_once($CFG->libdir.'/externallib.php');
 
diff --git a/tests/privacy/provider_test.php b/tests/privacy/provider_test.php
index ce1e349..8478f7e 100644
--- a/tests/privacy/provider_test.php
+++ b/tests/privacy/provider_test.php
@@ -29,12 +29,12 @@
  * @copyright   2018 David Mudrak <david@moodle.com>
  * @license     http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class provider_test extends \advanced_testcase {
+final class provider_test extends \advanced_testcase {
 
     /**
      * Assert that provider::get_metadata() returns valid content.
      */
-    public function test_get_metadata() {
+    public function test_get_metadata(): void {
 
         $items = new collection('editor_marklar');
         $result = provider::get_metadata($items);
@@ -45,7 +45,7 @@ public function test_get_metadata() {
     /**
      * Assert that provider::export_user_preferences() gives no data if the user has no Marklar preferences.
      */
-    public function test_export_user_preferences_no_pref() {
+    public function test_export_user_preferences_no_pref(): void {
 
         $user = \core_user::get_user_by_username('admin');
         provider::export_user_preferences($user->id);
@@ -58,7 +58,7 @@ public function test_export_user_preferences_no_pref() {
     /**
      * Assert that provider::export_user_preferences() gives user's Marklar preferences if they exist.
      */
-    public function test_export_user_preferences_has_pref() {
+    public function test_export_user_preferences_has_pref(): void {
         $this->resetAfterTest();
 
         $user = \core_user::get_user_by_username('admin');