diff --git a/lib/classes/component.php b/lib/classes/component.php
index 258d7eb25a2..f4e188bbb1b 100644
--- a/lib/classes/component.php
+++ b/lib/classes/component.php
@@ -172,6 +172,38 @@ class core_component {
             require($file);
             return;
         }
+
+        if (PHPUNIT_TEST) {
+            // For unit tests we support classes in `\frankenstyle_component\tests\` to be loaded from
+            // `path/to/frankenstyle/component/tests/classes` directory.
+            // Note: We do *not* support the legacy `\frankenstyle_component_tests_style_classnames`.
+            if ($component = self::get_component_from_classname($classname)) {
+                $pathoptions = [
+                    '/tests/classes' => "{$component}\\tests\\",
+                    '/tests/behat' => "{$component}\\behat\\",
+                ];
+                foreach ($pathoptions as $path => $testnamespace) {
+                    if (preg_match("#^" . preg_quote($testnamespace) . "#", $classname)) {
+                        $path = self::get_component_directory($component) . $path;
+                        $relativeclassname = str_replace(
+                            $testnamespace,
+                            '',
+                            $classname,
+                        );
+                        $file = sprintf(
+                            "%s/%s.php",
+                            $path,
+                            str_replace('\\', '/', $relativeclassname),
+                        );
+                        if (!empty($file) && file_exists($file)) {
+                            require($file);
+                            return;
+                        }
+                        break;
+                    }
+                }
+            }
+        }
     }
 
     /**
diff --git a/lib/phpunit/classes/util.php b/lib/phpunit/classes/util.php
index 0e0bb2d1cb6..1ad2fde17a6 100644
--- a/lib/phpunit/classes/util.php
+++ b/lib/phpunit/classes/util.php
@@ -529,6 +529,7 @@ class phpunit_util extends testing_util {
         $template = <<<EOF
             <testsuite name="@component@_testsuite">
               <directory suffix="_test.php">@dir@</directory>
+              <exclude>@dir@/classes</exclude>
             </testsuite>
 
         EOF;
@@ -621,6 +622,7 @@ class phpunit_util extends testing_util {
             <testsuites>
               <testsuite name="@component@_testsuite">
                 <directory suffix="_test.php">.</directory>
+                <exclude>./classes</exclude>
               </testsuite>
             </testsuites>
           EOT;
diff --git a/lib/tests/component_test.php b/lib/tests/component_test.php
index 74d372b3846..4a0974980d3 100644
--- a/lib/tests/component_test.php
+++ b/lib/tests/component_test.php
@@ -34,6 +34,14 @@ final class component_test extends advanced_testcase {
      */
     const SUBSYSTEMCOUNT = 77;
 
+    #[\Override]
+    public function tearDown(): void {
+        parent::tearDown();
+
+        $plugintypes = new ReflectionProperty(\core_component::class, 'plugintypes');
+        $plugintypes->setValue(null, null);
+    }
+
     public function test_get_core_subsystems(): void {
         global $CFG;
 
@@ -829,66 +837,66 @@ final class component_test extends advanced_testcase {
           'overlap'   => 'lib/tests/fixtures/component/overlap',
         ];
         return [
-          'PSR-0 Classloading - Root' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr0_main',
-              'file' => "{$directory}psr0/main.php",
-          ],
-          'PSR-0 Classloading - Sub namespace - underscores' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr0_subnamespace_example',
-              'file' => "{$directory}psr0/subnamespace/example.php",
-          ],
-          'PSR-0 Classloading - Sub namespace - slashes' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr0\\subnamespace\\slashes',
-              'file' => "{$directory}psr0/subnamespace/slashes.php",
-          ],
-          'PSR-0 Classloading - non-existent file' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr0_subnamespace_nonexistent_file',
-              'file' => false,
-          ],
-          'PSR-4 Classloading - Root' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr4\\main',
-              'file' => "{$directory}psr4/main.php",
-          ],
-          'PSR-4 Classloading - Sub namespace' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr4\\subnamespace\\example',
-              'file' => "{$directory}psr4/subnamespace/example.php",
-          ],
-          'PSR-4 Classloading - Ensure underscores are not converted to paths' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr4\\subnamespace\\underscore_example',
-              'file' => "{$directory}psr4/subnamespace/underscore_example.php",
-          ],
-          'PSR-4 Classloading - non-existent file' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'psr4\\subnamespace\\nonexistent',
-              'file' => false,
-          ],
-          'Overlap - Ensure no unexpected problems with PSR-4 when overlapping namespaces.' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'overlap\\subnamespace\\example',
-              'file' => "{$directory}overlap/subnamespace/example.php",
-          ],
-          'Overlap - Ensure no unexpected problems with PSR-0 overlapping namespaces.' => [
-              'psr0' => $psr0,
-              'psr4' => $psr4,
-              'classname' => 'overlap_subnamespace_example2',
-              'file' => "{$directory}overlap/subnamespace/example2.php",
-          ],
+            'PSR-0 Classloading - Root' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr0_main',
+                'file' => "{$directory}psr0/main.php",
+            ],
+            'PSR-0 Classloading - Sub namespace - underscores' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr0_subnamespace_example',
+                'file' => "{$directory}psr0/subnamespace/example.php",
+            ],
+            'PSR-0 Classloading - Sub namespace - slashes' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr0\\subnamespace\\slashes',
+                'file' => "{$directory}psr0/subnamespace/slashes.php",
+            ],
+            'PSR-0 Classloading - non-existent file' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr0_subnamespace_nonexistent_file',
+                'file' => false,
+            ],
+            'PSR-4 Classloading - Root' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr4\\main',
+                'file' => "{$directory}psr4/main.php",
+            ],
+            'PSR-4 Classloading - Sub namespace' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr4\\subnamespace\\example',
+                'file' => "{$directory}psr4/subnamespace/example.php",
+            ],
+            'PSR-4 Classloading - Ensure underscores are not converted to paths' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr4\\subnamespace\\underscore_example',
+                'file' => "{$directory}psr4/subnamespace/underscore_example.php",
+            ],
+            'PSR-4 Classloading - non-existent file' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'psr4\\subnamespace\\nonexistent',
+                'file' => false,
+            ],
+            'Overlap - Ensure no unexpected problems with PSR-4 when overlapping namespaces.' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'overlap\\subnamespace\\example',
+                'file' => "{$directory}overlap/subnamespace/example.php",
+            ],
+            'Overlap - Ensure no unexpected problems with PSR-0 overlapping namespaces.' => [
+                'psr0' => $psr0,
+                'psr4' => $psr4,
+                'classname' => 'overlap_subnamespace_example2',
+                'file' => "{$directory}overlap/subnamespace/example2.php",
+            ],
             'PSR-4 namespaces can come from multiple sources - first source' => [
                 'psr0' => $psr0,
                 'psr4' => [
@@ -914,6 +922,64 @@ final class component_test extends advanced_testcase {
         ];
     }
 
+    /**
+     * Test that the classloader can load from the test namespaces.
+     */
+    public function test_classloader_tests_namespace(): void {
+        global $CFG;
+
+        $this->resetAfterTest();
+
+        $getclassfilecontent = function (string $classname, ?string $namespace): string {
+            if ($namespace) {
+                $content = "<?php\nnamespace $namespace;\nclass $classname {}";
+            } else {
+                $content = "<?php\nclass $classname {}";
+            }
+            return $content;
+        };
+
+        $vfileroot = \org\bovigo\vfs\vfsStream::setup('root', null, [
+            'lib' => [
+                'classes' => [
+                    'example.php' => $getclassfilecontent('example', 'core'),
+                ],
+                'tests' => [
+                    'classes' => [
+                        'example_classname.php' => $getclassfilecontent('example_classname', \core\tests::class),
+                    ],
+                    'behat' => [
+                        'example_classname.php' => $getclassfilecontent('example_classname', \core\behat::class),
+                    ],
+                ],
+            ],
+        ]);
+
+        // Note: This is pretty hacky, but it's the only way to test the classloader.
+        // We have to override the dirroot and libdir, and then reset the plugintypes property.
+        $CFG->dirroot = $vfileroot->url();
+        $CFG->libdir = $vfileroot->url() . '/lib';
+        (new ReflectionProperty('core_component', 'plugintypes'))->setValue(null, null);
+
+        // Existing classes do not break.
+        $this->assertTrue(
+            class_exists(\core\example::class),
+        );
+
+        // Test and behat classes work.
+        $this->assertTrue(
+            class_exists(\core\tests\example_classname::class),
+        );
+        $this->assertTrue(
+            class_exists(\core\behat\example_classname::class),
+        );
+
+        // Non-existent classes do not do anything.
+        $this->assertFalse(
+            class_exists(\core\tests\example_classname_not_found::class),
+        );
+    }
+
     /**
      * Test the PSR classloader.
      *
diff --git a/lib/upgrade.txt b/lib/upgrade.txt
index ce3d25e93cf..fb0f2996c71 100644
--- a/lib/upgrade.txt
+++ b/lib/upgrade.txt
@@ -5,6 +5,7 @@ information provided here is intended especially for developers.
 
 * The `\core\dataformat::get_format_instance` method is now public, and can be used to retrieve a writer instance for
   a given dataformat
+* Added the ability for unit tests to autoload classes in the `\[component]\tests\` namespace from the `[path/to/component]/tests/classes` directory.
 
 === 4.4.1 ===
 
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index fd7faeecc08..de77041fcf2 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -35,54 +35,74 @@
   <testsuites>
     <testsuite name="core_phpunit_testsuite">
       <directory suffix="_test.php">lib/phpunit/tests</directory>
+      <exclude>lib/phpunit/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_test_testsuite">
       <directory suffix="_test.php">lib/testing/tests</directory>
+      <exclude>lib/testing/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_ddl_testsuite">
       <directory suffix="_test.php">lib/ddl/tests</directory>
+      <exclude>lib/ddl/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_dml_testsuite">
       <directory suffix="_test.php">lib/dml/tests</directory>
+      <exclude>lib/dml/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_testsuite">
       <directory suffix="_test.php">lib/tests</directory>
+      <exclude>lib/tests/classes</exclude>
       <!-- <directory suffix="_test.php">lib/ajax/tests</directory> -->
     </testsuite>
     <testsuite name="core_external_testsuite">
       <directory suffix="_test.php">lib/external/tests</directory>
+      <exclude>lib/external/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_favourites_testsuite">
       <directory suffix="_test.php">favourites/tests</directory>
+      <exclude>favourites/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_form_testsuite">
       <directory suffix="_test.php">lib/form/tests</directory>
+      <exclude>lib/form/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_files_testsuite">
       <directory suffix="_test.php">lib/filestorage/tests</directory>
       <directory suffix="_test.php">lib/filebrowser/tests</directory>
       <directory suffix="_test.php">files/tests</directory>
+      <exclude>lib/filestorage/tests/classes</exclude>
+      <exclude>lib/filebrowser/tests/classes</exclude>
+      <exclude>files/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_filter_testsuite">
       <directory suffix="_test.php">filter/tests</directory>
+      <exclude>filter/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_role_testsuite">
       <directory suffix="_test.php">admin/roles/tests</directory>
+      <exclude>admin/roles/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_cohort_testsuite">
       <directory suffix="_test.php">cohort/tests</directory>
+      <exclude>cohort/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_grades_testsuite">
       <directory suffix="_test.php">lib/grade/tests</directory>
       <directory suffix="_test.php">grade/tests</directory>
       <directory suffix="_test.php">grade/grading/tests</directory>
       <directory suffix="_test.php">grade/import/csv/tests</directory>
+      <exclude>lib/grade/tests/classes</exclude>
+      <exclude>grade/tests/classes</exclude>
+      <exclude>grade/grading/tests/classes</exclude>
+      <exclude>grade/import/csv/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_analytics_testsuite">
       <directory suffix="_test.php">analytics/tests</directory>
+      <exclude>analytics/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_availability_testsuite">
       <directory suffix="_test.php">availability/tests</directory>
+      <exclude>availability/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_backup_testsuite">
       <directory suffix="_test.php">backup/controller/tests</directory>
@@ -90,135 +110,185 @@
       <directory suffix="_test.php">backup/moodle2/tests</directory>
       <directory suffix="_test.php">backup/tests</directory>
       <directory suffix="_test.php">backup/util</directory>
+      <exclude>backup/controller/tests/classes</exclude>
+      <exclude>backup/converter/moodle1/tests/classes</exclude>
+      <exclude>backup/moodle2/tests/classes</exclude>
+      <exclude>backup/tests/classes</exclude>
+      <exclude>backup/util/classes</exclude>
     </testsuite>
     <testsuite name="core_badges_testsuite">
       <directory suffix="_test.php">badges/tests</directory>
+      <exclude>badges/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_blog_testsuite">
       <directory suffix="_test.php">blog/tests</directory>
+      <exclude>blog/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_customfield_testsuite">
       <directory suffix="_test.php">customfield/tests</directory>
+      <exclude>customfield/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_iplookup_testsuite">
       <directory suffix="_test.php">iplookup/tests</directory>
+      <exclude>iplookup/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_course_testsuite">
       <directory suffix="_test.php">course/tests</directory>
+      <exclude>course/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_courseformat_testsuite">
       <directory suffix="_test.php">course/format/tests</directory>
+      <exclude>course/format/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_privacy_testsuite">
       <directory suffix="_test.php">privacy/tests</directory>
+      <exclude>privacy/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_question_testsuite">
       <directory suffix="_test.php">question/engine/tests</directory>
       <directory suffix="_test.php">question/tests</directory>
       <directory suffix="_test.php">question/type/tests</directory>
       <directory suffix="_test.php">question/engine/upgrade/tests</directory>
+      <exclude>question/engine/tests/classes</exclude>
+      <exclude>question/tests/classes</exclude>
+      <exclude>question/type/tests/classes</exclude>
+      <exclude>question/engine/upgrade/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_cache_testsuite">
       <directory suffix="_test.php">cache/tests</directory>
+      <exclude>cache/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_calendar_testsuite">
       <directory suffix="_test.php">calendar/tests</directory>
+      <exclude>calendar/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_enrol_testsuite">
       <directory suffix="_test.php">enrol/tests</directory>
+      <exclude>enrol/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_group_testsuite">
       <directory suffix="_test.php">group/tests</directory>
+      <exclude>group/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_message_testsuite">
       <directory suffix="_test.php">message/tests</directory>
+      <exclude>message/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_notes_testsuite">
       <directory suffix="_test.php">notes/tests</directory>
+      <exclude>notes/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_tag_testsuite">
       <directory suffix="_test.php">tag/tests</directory>
+      <exclude>tag/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_rating_testsuite">
       <directory suffix="_test.php">rating/tests</directory>
+      <exclude>rating/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_repository_testsuite">
       <directory suffix="_test.php">repository/tests</directory>
+      <exclude>repository/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_userkey_testsuite">
       <directory suffix="_test.php">lib/userkey/tests</directory>
+      <exclude>lib/userkey/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_user_testsuite">
       <directory suffix="_test.php">user/tests</directory>
+      <exclude>user/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_webservice_testsuite">
       <directory suffix="_test.php">webservice/tests</directory>
+      <exclude>webservice/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_mnet_testsuite">
       <directory suffix="_test.php">mnet/tests</directory>
+      <exclude>mnet/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_completion_testsuite">
       <directory suffix="_test.php">completion/tests</directory>
+      <exclude>completion/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_comment_testsuite">
       <directory suffix="_test.php">comment/tests</directory>
+      <exclude>comment/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_search_testsuite">
       <directory suffix="_test.php">search/tests</directory>
+      <exclude>search/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_competency_testsuite">
       <directory suffix="_test.php">competency/tests</directory>
+      <exclude>competency/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_my_testsuite">
       <directory suffix="_test.php">my/tests</directory>
+      <exclude>my/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_auth_testsuite">
       <directory suffix="_test.php">auth/tests</directory>
+      <exclude>auth/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_block_testsuite">
       <directory suffix="_test.php">blocks/tests</directory>
+      <exclude>blocks/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_login_testsuite">
       <directory suffix="_test.php">login/tests</directory>
+      <exclude>login/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_plagiarism_testsuite">
       <directory suffix="_test.php">plagiarism/tests</directory>
+      <exclude>plagiarism/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_portfolio_testsuite">
       <directory suffix="_test.php">portfolio/tests</directory>
+      <exclude>portfolio/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_editor_testsuite">
       <directory suffix="_test.php">lib/editor/tests</directory>
+      <exclude>lib/editor/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_rss_testsuite">
       <directory suffix="_test.php">rss/tests</directory>
+      <exclude>rss/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_table_testsuite">
       <directory suffix="_test.php">lib/table/tests</directory>
+      <exclude>lib/table/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_h5p_testsuite">
       <directory suffix="_test.php">h5p/tests</directory>
+      <exclude>h5p/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_xapi_testsuite">
       <directory suffix="_test.php">lib/xapi/tests</directory>
+      <exclude>lib/xapi/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_contentbank_testsuite">
       <directory suffix="_test.php">contentbank/tests</directory>
+      <exclude>contentbank/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_payment_testsuite">
       <directory suffix="_test.php">payment/tests</directory>
+      <exclude>payment/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_reportbuilder_testsuite">
       <directory suffix="_test.php">reportbuilder/tests</directory>
+      <exclude>reportbuilder/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_adminpresets_testsuite">
       <directory suffix="_test.php">admin/presets/tests</directory>
+      <exclude>admin/presets/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_admin_testsuite">
       <directory suffix="_test.php">admin/tests</directory>
+      <exclude>admin/tests/classes</exclude>
     </testsuite>
     <testsuite name="core_communication_testsuite">
       <directory suffix="_test.php">communication/tests</directory>
+      <exclude>communication/tests/classes</exclude>
     </testsuite>
 
     <!--Plugin suites: use admin/tool/phpunit/cli/util.php to build phpunit.xml from