diff --git a/.ddev/config.wunderio.yaml b/.ddev/config.wunderio.yaml
index 6548d872..8d62501e 100644
--- a/.ddev/config.wunderio.yaml
+++ b/.ddev/config.wunderio.yaml
@@ -13,7 +13,7 @@ hooks:
     # @todo We could potentially make this work from recognizing the command.
     - exec: |
         if ! command -v wdr-core &> /dev/null; then
-          ln -s ${HOME}/wunderio/core/wdr-core.sh /usr/local/bin/wdr-core
+          sudo ln -s ${HOME}/wunderio/core/wdr-core.sh /usr/local/bin/wdr-core
         fi
         # Run once start hook if needed
         if [ ! -f "/mnt/wdr-hooks/ddev_web_post_start_once" ]; then
diff --git a/composer.json b/composer.json
index 79d2d6c9..168b3455 100644
--- a/composer.json
+++ b/composer.json
@@ -34,7 +34,7 @@
     },
     "require-dev": {
         "drupal/core-dev": "^11.4",
-        "wunderio/code-quality": "^3.0"
+        "wunderio/code-quality": "dev-GH-126-php"
     },
     "conflict": {
         "drupal/drupal": "*"
diff --git a/phpunit.xml b/phpunit.xml
index 796cbbc7..7500a113 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -49,19 +49,12 @@
   <!-- Filter for coverage reports. -->
   <source>
     <include>
-      <directory>./web/core/includes</directory>
-      <directory>./web/core/lib</directory>
-      <directory>./web/core/modules</directory>
-      <directory>./web/core/modules</directory>
-      <directory>./web/core/sites</directory>
+      <directory>./web/modules/custom</directory>
+      <directory>./web/themes/custom</directory>
     </include>
     <exclude>
-      <directory>./web/core/modules/*/src/Tests</directory>
-      <directory>./web/core/modules/*/tests</directory>
-      <directory>./web/core/modules/*/src/Tests</directory>
-      <directory>./web/core/modules/*/tests</directory>
-      <directory>./web/core/modules/*/*/src/Tests</directory>
-      <directory>./web/core/modules/*/*/tests</directory>
+      <directory>./web/modules/custom/*/tests</directory>
+      <directory>./web/themes/custom/*/tests</directory>
     </exclude>
   </source>
 </phpunit>
diff --git a/web/modules/custom/phpunit_example/phpunit_example.info.yml b/web/modules/custom/phpunit_example/phpunit_example.info.yml
index 4a9eea2d..52abee45 100644
--- a/web/modules/custom/phpunit_example/phpunit_example.info.yml
+++ b/web/modules/custom/phpunit_example/phpunit_example.info.yml
@@ -2,6 +2,4 @@ name: PHPUnit Example
 type: module
 description: Demonstrates how to use PHPUnit-based tests.
 package: Example modules
-core_version_requirement: ^10 || ^11
-dependencies:
-  - drupal:node
+core_version_requirement: ^11
diff --git a/web/modules/custom/phpunit_example/phpunit_example.module b/web/modules/custom/phpunit_example/phpunit_example.module
index b02383de..aeeb7b02 100644
--- a/web/modules/custom/phpunit_example/phpunit_example.module
+++ b/web/modules/custom/phpunit_example/phpunit_example.module
@@ -9,7 +9,7 @@
  * @defgroup phpunit_example Example: PHPUnit
  * @ingroup examples
  * @{
- * This example demonstrates PHPUnit for Drupal 8 unit testing.
+ * This example demonstrates PHPUnit for Drupal unit testing.
  */
 
 /**
diff --git a/web/modules/custom/phpunit_example/src/AddClass.php b/web/modules/custom/phpunit_example/src/AddClass.php
index c60481ad..5443c79f 100644
--- a/web/modules/custom/phpunit_example/src/AddClass.php
+++ b/web/modules/custom/phpunit_example/src/AddClass.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\phpunit_example;
 
 /**
@@ -12,9 +14,13 @@ class AddClass {
   /**
    * A simple addition method with validity checking.
    *
-   * @param int|float $a
+   * The parameters are typed as `mixed` (rather than `int|float`) on
+   * purpose, so that non-numeric values reach the validity check below and
+   * trigger an \InvalidArgumentException instead of a \TypeError.
+   *
+   * @param mixed $a
    *   A number to add.
-   * @param int|float $b
+   * @param mixed $b
    *   Another number to add.
    *
    * @return int|float
@@ -23,7 +29,7 @@ class AddClass {
    * @throws \InvalidArgumentException
    *   If either $a or $b is non-numeric, we can't add, so we throw.
    */
-  public function add($a, $b) {
+  public function add(mixed $a, mixed $b): int|float {
     // Check whether the arguments are numeric.
     foreach ([$a, $b] as $argument) {
       if (!is_numeric($argument)) {
diff --git a/web/modules/custom/phpunit_example/tests/src/Unit/AddClassTest.php b/web/modules/custom/phpunit_example/tests/src/Unit/AddClassTest.php
index 264ac41d..c479af30 100644
--- a/web/modules/custom/phpunit_example/tests/src/Unit/AddClassTest.php
+++ b/web/modules/custom/phpunit_example/tests/src/Unit/AddClassTest.php
@@ -1,38 +1,43 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\Tests\phpunit_example\Unit;
 
 use Drupal\phpunit_example\AddClass;
 // phpcs:ignore SlevomatCodingStandard.Namespaces.AlphabeticallySortedUses.IncorrectlyOrderedUses
 use Drupal\Tests\UnitTestCase;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Group;
 
 /**
- * AddClass units tests.
+ * AddClass unit tests.
  *
- * This test case demonstrates the following PHPUnit annotations:
- * - dataProvider
- * - expectedException.
+ * This test case demonstrates the following PHPUnit 11 features:
+ * - Attribute-based data providers (#[DataProvider]).
+ * - Attribute-based grouping (#[Group]).
+ * - expectException() for exception assertions.
  *
- * PHPUnit looks for classes with names ending in 'Test'. Then it
- * looks to see whether that class is a subclass of
- * \PHPUnit_Framework_TestCase. Drupal supplies us with
- * Drupal\Tests\UnitTestCase, which is a subclass of
- * \PHPUnit_Framework_TestCase. So yay, PHPUnit will find this class.
+ * PHPUnit discovers test classes by their 'Test' suffix and requires them
+ * to extend \PHPUnit\Framework\TestCase. Drupal supplies
+ * \Drupal\Tests\UnitTestCase, a subclass of \PHPUnit\Framework\TestCase,
+ * which this class extends.
  *
- * In unit testing, there should be as few dependencies as possible.
- * We want the smallest number of moving parts to be interacting in
- * our test, or we won't be sure where the errors are, or whether our
- * tests passed by accident.
+ * In unit testing, there should be as few dependencies as possible. We
+ * want the smallest number of moving parts to be interacting in our test,
+ * or we won't be sure where the errors are, or whether our tests passed by
+ * accident.
  *
- * So with that in mind, it's up to us to build out whatever
- * dependencies we need. In the case of AddClass, our needs are meager;
- * we only want an instance of AddClass so we can test its add() method.
+ * So with that in mind, it's up to us to build out whatever dependencies we
+ * need. In the case of AddClass, our needs are meager; we only want an
+ * instance of AddClass so we can test its add() method.
  *
  * @ingroup phpunit_example
- *
- * @group phpunit_example
- * @group examples
  */
+#[CoversClass(AddClass::class)]
+#[Group('phpunit_example')]
+#[Group('examples')]
 class AddClassTest extends UnitTestCase {
 
   /**
@@ -43,19 +48,20 @@ class AddClassTest extends UnitTestCase {
    * pass. It ignores most of the problems that could arise in the
    * method under test, so therefore: It is not a very good test.
    */
-  public function testAdd() {
+  public function testAdd(): void {
     $sut = new AddClass();
-    $this->assertEquals($sut->add(2, 3), 5);
+    $this->assertEquals(5, $sut->add(2, 3));
   }
 
+  #[DataProvider('addDataProvider')]
   /**
    * Test AddClass::add() with a data provider method.
    *
-   * This method is very similar to testAdd(), but uses a data provider method
-   * to test with a wider range of data.
+   * This method is very similar to testAdd(), but uses a data provider
+   * method to test with a wider range of data.
    *
    * You can tell PHPUnit which method is the data provider using the
-   * '@dataProvider' annotation.
+   * '#[DataProvider]' attribute.
    *
    * The data provider method just returns a big array of arrays of arguments.
    * That is, for each time you want this test method run, the data provider
@@ -80,36 +86,29 @@ public function testAdd() {
    * tests 'good' data. When combined with testAddWithBadDataProvider(),
    * we get a better picture of the behavior of the method under test.
    *
-   * @dataProvider addDataProvider
-   *
    * @see self::addDataProvider()
    */
-  public function testAddWithDataProvider($expected, $a, $b) {
+  public function testAddWithDataProvider(int|float $expected, int|float $a, int|float $b): void {
     $sut = new AddClass();
     $this->assertEquals($expected, $sut->add($a, $b));
   }
 
+  #[DataProvider('addBadDataProvider')]
   /**
    * Test AddClass::add() with data that should throw an exception.
    *
    * This method is similar to testAddWithDataProvider(), but the data
    * provider gives us data that should throw an exception.
    *
-   * This test uses the setExpectedException() method to tell PHPUnit that
-   * a thrown exception should pass the test. You specify a
-   * fully-qualified exception class name. If you specify \Exception, PHPUnit
-   * will pass any exception, whereas a more specific subclass of \Exception
-   * will require that exception type to be thrown.
-   *
-   * Alternately, you can use try and catch blocks with assertions in order
-   * to test exceptions. We won't demonstrate that here; it's a much better
-   * idea to test your exceptions with setExpectedException().
-   *
-   * @dataProvider addBadDataProvider
+   * This test uses the expectException() method to tell PHPUnit that a
+   * thrown exception should pass the test. You specify a fully-qualified
+   * exception class name. If you specify \Exception, PHPUnit will pass any
+   * exception, whereas a more specific subclass of \Exception will require
+   * that exception type to be thrown.
    *
    * @see self::addBadDataProvider()
    */
-  public function testAddWithBadDataProvider($a, $b) {
+  public function testAddWithBadDataProvider(mixed $a, mixed $b): void {
     $sut = new AddClass();
     $this->expectException(\InvalidArgumentException::class);
     $sut->add($a, $b);
@@ -135,7 +134,7 @@ public function testAddWithBadDataProvider($a, $b) {
    *
    * @see self::testAddWithDataProvider()
    */
-  public static function addDataProvider() {
+  public static function addDataProvider(): array {
     return [
       [5, 2, 3],
       [50, 20, 30],
@@ -154,7 +153,7 @@ public static function addDataProvider() {
    *
    * @see self::testAddWithBadDataProvider()
    */
-  public static function addBadDataProvider() {
+  public static function addBadDataProvider(): array {
     $bad_data = [];
     // Set up an array with data that should cause add()
     // to throw an exception.