diff --git a/.upgradenotes/MDL-86311-2025081418402045.yml b/.upgradenotes/MDL-86311-2025081418402045.yml
new file mode 100644
index 00000000000..3b86b7cea70
--- /dev/null
+++ b/.upgradenotes/MDL-86311-2025081418402045.yml
@@ -0,0 +1,13 @@
+issueNumber: MDL-86311
+notes:
+  core:
+    - message: >-
+        The default PHPUnit configuration now enables the following properties,
+        ensuring PHP warnings will cause test failures (restoring pre-PHPUnit
+        version 10 behaviour):
+
+
+        * `failOnDeprecation`
+
+        * `failOnWarning`
+      type: changed
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index f0ecc67bd16..90b9dea5f03 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -6,6 +6,8 @@
   processIsolation="false"
   backupGlobals="false"
   cacheResult="false"
+  failOnDeprecation="true"
+  failOnWarning="true"
   stopOnError="false"
   stopOnFailure="false"
   stopOnIncomplete="false"
diff --git a/public/lib/classes/router/util.php b/public/lib/classes/router/util.php
index eada7c17d8b..1c2011feeda 100644
--- a/public/lib/classes/router/util.php
+++ b/public/lib/classes/router/util.php
@@ -293,14 +293,11 @@ class util {
     public static function normalise_component_path(
         string $component,
     ): string {
-        if ($component === 'core') {
-            return $component;
-        }
         [$type, $subsystem] = \core\component::normalize_component($component);
-        if ($type === 'core') {
+        if ($type === 'core' && $subsystem !== null) {
             return str_replace('core_', '', $subsystem);
         }
 
-        return $component ?? '';
+        return $component;
     }
 }
diff --git a/public/question/type/multianswer/tests/question_type_test.php b/public/question/type/multianswer/tests/question_type_test.php
index b7e33f99d06..b184fc1e946 100644
--- a/public/question/type/multianswer/tests/question_type_test.php
+++ b/public/question/type/multianswer/tests/question_type_test.php
@@ -447,6 +447,7 @@ final class question_type_test extends \advanced_testcase {
         $this->resetAfterTest(true);
         $this->setAdminUser();
 
+        /** @var \core_question_generator $generator */
         $generator = $this->getDataGenerator()->get_plugin_generator('core_question');
         $cat = $generator->create_question_category([]);
         $question = $generator->create_question('multianswer', 'twosubq', ['category' => $cat->id]);
@@ -465,6 +466,7 @@ final class question_type_test extends \advanced_testcase {
         $editedquestion = test_question_maker::get_question_data('multianswer', 'twosubq');
         $editedquestion->id = $question->id;
         $editedquestion->category = $cat->id;
+        $editedquestion->context = \context_helper::instance_by_id($cat->contextid);
         $editedsubq1 = test_question_maker::get_question_form_data('multichoice', 'one_of_four');
         $editedsubq1->id = $originalsubq1->id;
         $editedsubq1->qtype = 'multichoice';
diff --git a/public/question/type/multichoice/tests/restore_test.php b/public/question/type/multichoice/tests/restore_test.php
index 3092ab1d24e..ae377de8348 100644
--- a/public/question/type/multichoice/tests/restore_test.php
+++ b/public/question/type/multichoice/tests/restore_test.php
@@ -48,7 +48,7 @@ final class restore_test extends \advanced_testcase {
         $cat = $questiongenerator->create_question_category(['contextid' => $context->id]);
 
         // Create a quiz containing a multichoice question from the qbank.
-        $quiz = $this->getDataGenerator()->get_plugin_generator('quiz')->create_instance(['course' => $course1->id]);
+        $quiz = $this->getDataGenerator()->get_plugin_generator('mod_quiz')->create_instance(['course' => $course1->id]);
         $question = $questiongenerator->create_question('multichoice', 'one_of_four', ['category' => $cat->id]);
         quiz_add_quiz_question($question->id, $quiz);
 
@@ -72,6 +72,13 @@ final class restore_test extends \advanced_testcase {
         $rc->execute_plan();
         $rc->destroy();
 
+        // Executing the precheck and plan will each emit debugging related to missing options.
+        $this->assertDebuggingCalledCount(
+            2,
+            array_fill(0, 2, "Question ID {$question->id} was missing an options record. Using default."),
+            array_fill(0, 2, DEBUG_DEVELOPER),
+        );
+
         // Both quizzes should refer to the same original question.
         $quizzes = get_fast_modinfo($course1->id)->get_instances_of('quiz');
         $this->assertCount(2, $quizzes);
diff --git a/public/question/type/numerical/tests/restore_test.php b/public/question/type/numerical/tests/restore_test.php
index 57aa65fd647..9367c1d3a76 100644
--- a/public/question/type/numerical/tests/restore_test.php
+++ b/public/question/type/numerical/tests/restore_test.php
@@ -48,7 +48,7 @@ final class restore_test extends \advanced_testcase {
         $cat = $questiongenerator->create_question_category(['contextid' => $context->id]);
 
         // Create a quiz containing a multichoice question from the qbank.
-        $quiz = $this->getDataGenerator()->get_plugin_generator('quiz')->create_instance(['course' => $course1->id]);
+        $quiz = $this->getDataGenerator()->get_plugin_generator('mod_quiz')->create_instance(['course' => $course1->id]);
         $question = $questiongenerator->create_question('numerical', 'pi', ['category' => $cat->id]);
         quiz_add_quiz_question($question->id, $quiz);