diff --git a/tests/phpunit/base_testcase.php b/tests/phpunit/base_testcase.php
index b4f030e..1204420 100644
--- a/tests/phpunit/base_testcase.php
+++ b/tests/phpunit/base_testcase.php
@@ -68,7 +68,7 @@ abstract class auth_outage_base_testcase extends advanced_testcase {
     /**
      * Setup testcase.
      */
-    public function setUp() {
+    public function setUp(): void {
         global $CFG;
 
         parent::setUp();
diff --git a/tests/phpunit/dml/outagedb_test.php b/tests/phpunit/dml/outagedb_test.php
index af9af0c..e10eb08 100644
--- a/tests/phpunit/dml/outagedb_test.php
+++ b/tests/phpunit/dml/outagedb_test.php
@@ -78,7 +78,7 @@ class outagedb_test extends auth_outage_base_testcase {
     /**
      * Ensure DB tests run as admin.
      */
-    public function setUp() {
+    public function setUp(): void {
         parent::setUp();
         $this->setAdminUser();
     }
diff --git a/tests/phpunit/local/cli/cli_testcase.php b/tests/phpunit/local/cli/cli_testcase.php
index 88aa77f..6e082ce 100644
--- a/tests/phpunit/local/cli/cli_testcase.php
+++ b/tests/phpunit/local/cli/cli_testcase.php
@@ -40,7 +40,7 @@ abstract class auth_outage_cli_testcase extends auth_outage_base_testcase {
     /**
      * Always enable the auth outage plugin, resets after test and set no parameters.
      */
-    public function setUp() {
+    public function setUp(): void {
         global $CFG;
 
         // PHPUnit does not load config.php file.