diff --git a/lib/phpunit/classes/advanced_testcase.php b/lib/phpunit/classes/advanced_testcase.php
index e18fddf3182..b65db0c2c98 100644
--- a/lib/phpunit/classes/advanced_testcase.php
+++ b/lib/phpunit/classes/advanced_testcase.php
@@ -63,7 +63,7 @@ abstract class advanced_testcase extends base_testcase {
      * Runs the bare test sequence.
      * @return void
      */
-    final public function runBare() {
+    final public function runBare(): void {
         global $DB;
 
         if (phpunit_util::$lastdbwrites != $DB->perf_get_writes()) {
diff --git a/lib/phpunit/classes/autoloader.php b/lib/phpunit/classes/autoloader.php
index c39ec4aac48..50052db4fd9 100644
--- a/lib/phpunit/classes/autoloader.php
+++ b/lib/phpunit/classes/autoloader.php
@@ -43,7 +43,7 @@
  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 class phpunit_autoloader implements \PHPUnit\Runner\TestSuiteLoader {
-    public function load($suiteClassName, $suiteClassFile = '') {
+    public function load(string $suiteClassName, string $suiteClassFile = ''): ReflectionClass {
         global $CFG;
 
         // Let's guess what user entered on the commandline...
@@ -197,7 +197,7 @@ class phpunit_autoloader implements \PHPUnit\Runner\TestSuiteLoader {
         return new ReflectionClass($classname);
     }
 
-    public function reload(ReflectionClass $aClass) {
+    public function reload(ReflectionClass $aClass): ReflectionClass {
         return $aClass;
     }
 }
diff --git a/lib/phpunit/classes/basic_testcase.php b/lib/phpunit/classes/basic_testcase.php
index ba7d000bf01..497f260bd90 100644
--- a/lib/phpunit/classes/basic_testcase.php
+++ b/lib/phpunit/classes/basic_testcase.php
@@ -57,7 +57,7 @@ abstract class basic_testcase extends base_testcase {
      * Runs the bare test sequence and log any changes in global state or database.
      * @return void
      */
-    final public function runBare() {
+    final public function runBare(): void {
         global $DB;
 
         try {
diff --git a/lib/phpunit/classes/database_driver_testcase.php b/lib/phpunit/classes/database_driver_testcase.php
index 5236a6e88fc..63a99d4d802 100644
--- a/lib/phpunit/classes/database_driver_testcase.php
+++ b/lib/phpunit/classes/database_driver_testcase.php
@@ -138,7 +138,7 @@ abstract class database_driver_testcase extends base_testcase {
      * Runs the bare test sequence.
      * @return void
      */
-    public function runBare() {
+    public function runBare(): void {
         try {
             parent::runBare();
 
diff --git a/lib/phpunit/classes/hint_resultprinter.php b/lib/phpunit/classes/hint_resultprinter.php
index fb10e5a5627..228db3e10a9 100644
--- a/lib/phpunit/classes/hint_resultprinter.php
+++ b/lib/phpunit/classes/hint_resultprinter.php
@@ -48,7 +48,7 @@ class Hint_ResultPrinter extends PHPUnit\TextUI\ResultPrinter {
         parent::__construct(null, false, self::COLOR_DEFAULT, false);
     }
 
-    protected function printDefectTrace(PHPUnit\Framework\TestFailure $defect) {
+    protected function printDefectTrace(PHPUnit\Framework\TestFailure $defect): void {
         global $CFG;
 
         parent::printDefectTrace($defect);
diff --git a/lib/tests/completionlib_test.php b/lib/tests/completionlib_test.php
index cc2dfbb57c2..1b4f163a949 100644
--- a/lib/tests/completionlib_test.php
+++ b/lib/tests/completionlib_test.php
@@ -76,7 +76,7 @@ class core_completionlib_testcase extends advanced_testcase {
      * @param  boolean $canonicalize
      * @param  boolean $ignoreCase
      */
-    public static function assertEquals($expected, $actual, $message = '', $delta = 0, $maxDepth = 10, $canonicalize = FALSE, $ignoreCase = FALSE) {
+    public static function assertEquals($expected, $actual, string $message = '', float $delta = 0, int $maxDepth = 10, bool $canonicalize = false, bool $ignoreCase = false): void {
         // Nasty cheating hack: prevent random failures on timemodified field.
         if (is_object($expected) and is_object($actual)) {
             if (property_exists($expected, 'timemodified') and property_exists($actual, 'timemodified')) {