diff --git a/riddler.info.yml b/riddler.info.yml
index 7c0e534..d6b9176 100644
--- a/riddler.info.yml
+++ b/riddler.info.yml
@@ -3,6 +3,7 @@ type: module
 description: 'Provides a question and answer CAPTCHA.'
 package: Spam control
 core: 8.x
+core_version_requirement: ^8 || ^9
 dependencies:
   - captcha:captcha
 configure: admin/config/people/riddler
diff --git a/src/Tests/RiddlerTestCase.php b/src/Tests/RiddlerTestCase.php
deleted file mode 100755
index ce95d27..0000000
--- a/src/Tests/RiddlerTestCase.php
+++ /dev/null
@@ -1,199 +0,0 @@
-<?php
-
-/**
- * Contains Drupal\captcha\Tests\CaptchaTestCase.
- */
-
-namespace Drupal\riddler\Tests;
-
-use Drupal\captcha\Tests\CaptchaBaseWebTestCase;
-
-/**
- * Tests Riddler main test case sensitivity.
- *
- * @group captcha
- */
-class RiddlerTestCase extends CaptchaBaseWebTestCase {
-
-  /**
-   * Modules to enable.
-   *
-   * @var array
-   */
-  public static $modules = ['block', 'comment', 'captcha', 'riddler'];
-
-//  /**
-//   * Testing the protection of the user log in form.
-//   */
-//  public function testCaptchaOnLoginForm() {
-//    // Create user and test log in without CAPTCHA.
-//    $user = $this->drupalCreateUser();
-//    $this->drupalLogin($user);
-//    // Log out again.
-//    $this->drupalLogout();
-//
-//    // Set a CAPTCHA on login form.
-//    /* @var \Drupal\captcha\Entity\CaptchaPoint $captcha_point */
-//    $captcha_point = \Drupal::entityManager()->getStorage('captcha_point')->load('user_login_form');
-//    $captcha_point->setCaptchaType('riddler/Riddler');
-//    $captcha_point->enable()->save();
-//
-//    // Check if there is a CAPTCHA on the login form (look for the title).
-//    $this->drupalGet('');
-//    $this->assertText('Do you really hate Spam?',
-//      'There should be a CAPTCHA Riddle on the form.', 'Riddler'
-//    );
-//
-//    // Try to log in, which should fail.
-//    $edit = [
-//      'name' => $user->getUsername(),
-//      'pass' => $user->pass_raw,
-//      'captcha_response' => '?',
-//    ];
-//    $this->drupalPostForm(NULL, $edit, t('Log in'), [], [], self::LOGIN_HTML_FORM_ID);
-//    // Check for error message.
-//    $this->assertText(self::CAPTCHA_WRONG_RESPONSE_ERROR_MESSAGE, 'Riddler should block user login form', 'Riddler');
-//
-//    // And make sure that user is not logged in:
-//    // check for name and password fields on ?q=user.
-//    $this->drupalGet('user');
-//    $this->assertField('name', t('Username field found.'), 'Riddler');
-//    $this->assertField('pass', t('Password field found.'), 'Riddler');
-//  }
-//
-//  /**
-//   * Assert function for testing if comment posting works as it should.
-//   *
-//   * Creates node with comment writing enabled, tries to post comment
-//   * with given CAPTCHA response (caller should enable the desired
-//   * challenge on page node comment forms) and checks if
-//   * the result is as expected.
-//   *
-//   * @param string $captcha_response
-//   *   The response on the CAPTCHA.
-//   * @param bool $should_pass
-//   *   Describing if the posting should pass or should be blocked.
-//   * @param string $message
-//   *   To prefix to nested asserts.
-//   */
-//  protected function assertCommentPosting($captcha_response, $should_pass, $message) {
-//    // Make sure comments on pages can be saved directly without preview.
-//    $this->container->get('state')->set('comment_preview_page', DRUPAL_OPTIONAL);
-//
-//    // Create a node with comments enabled.
-//    $node = $this->drupalCreateNode();
-//
-//    // Post comment on node.
-//    $edit = $this->getCommentFormValues();
-//    $comment_subject = $edit['subject[0][value]'];
-//    $comment_body = $edit['comment_body[0][value]'];
-//    $edit['captcha_response'] = $captcha_response;
-//    $this->drupalPostForm('comment/reply/node/' . $node->id() . '/comment', $edit, t('Save'), [], [], 'comment-form');
-//
-//    if ($should_pass) {
-//      // There should be no error message.
-//      $this->assertCaptchaResponseAccepted();
-//      // Get node page and check that comment shows up.
-//      $this->drupalGet('node/' . $node->id());
-//      $this->assertText($comment_subject, $message . ' Comment should show up on node page.', 'Riddler');
-//      $this->assertText($comment_body, $message . ' Comment should show up on node page.', 'Riddler');
-//    }
-//    else {
-//      // Check for error message.
-//      $this->assertText(self::CAPTCHA_WRONG_RESPONSE_ERROR_MESSAGE, $message . ' Comment submission should be blocked.', 'Riddler');
-//      // Get node page and check that comment is not present.
-//      $this->drupalGet('node/' . $node->id());
-//      $this->assertNoText($comment_subject, $message . ' Comment should not show up on node page.', 'Riddler');
-//      $this->assertNoText($comment_body, $message . ' Comment should not show up on node page.', 'Riddler');
-//    }
-//  }
-//
-//  /**
-//   * Testing the case sensitive/insensitive validation.
-//   */
-//  public function testCaseInsensitiveValidation() {
-//    $config = $this->config('captcha.settings');
-//    // Set Test CAPTCHA on comment form.
-//    captcha_set_form_id_setting(self::COMMENT_FORM_ID, 'riddler/Riddler');
-//
-//    // Log in as normal user.
-//    $this->drupalLogin($this->normalUser);
-//
-//    // Test case sensitive posting.
-//    $config->set('default_validation', CAPTCHA_DEFAULT_VALIDATION_CASE_SENSITIVE);
-//    $config->save();
-//
-//    $this->assertCommentPosting('Yes!', TRUE, 'Case sensitive validation of right casing.');
-//    $this->assertCommentPosting('yes!', FALSE, 'Case sensitive validation of wrong casing.');
-//    $this->assertCommentPosting('YES!', FALSE, 'Case sensitive validation of wrong casing.');
-//
-//    // Test case insensitive posting (the default).
-//    $config->set('default_validation', CAPTCHA_DEFAULT_VALIDATION_CASE_INSENSITIVE);
-//    $config->save();
-//
-//    $this->assertCommentPosting('Yes!', TRUE, 'Case insensitive validation of right casing.');
-//    $this->assertCommentPosting('yes!', TRUE, 'Case insensitive validation of wrong casing.');
-//    $this->assertCommentPosting('YES!', TRUE, 'Case insensitive validation of wrong casing.');
-//  }
-
-  /**
-   * Drupal path of the Riddler admin page.
-   */
-  const RIDDLER_ADMIN_PATH = 'admin/config/people/captcha/riddler';
-
-
-  /**
-   * Method for testing the Riddler riddles administration.
-   */
-  public function testRiddlesAdministration() {
-    $form_values_1_question = [
-      'riddler[0][question]' => 'What is your favorite primary color?',
-      'riddler[0][response]' => 'red, blue, yellow',
-    ];
-    $form_values_2_question = [
-      'riddler[0][question]' => 'What is your favorite primary color?',
-      'riddler[0][response]' => 'red, blue, yellow',
-      'riddler[1][question]' => 'What color is Druplicon?',
-      'riddler[1][response]' => 'blue',
-    ];
-
-    $addAnotherButton = ['op' => 'Add another riddle'];
-
-    $this->drupalLogin($this->adminUser);
-
-    // Check that the admin form exists.
-    $this->drupalGet(self::RIDDLER_ADMIN_PATH);
-    $this->assertText(t('Add questions that you require users to answer.'),
-      'Admin should be able to see the Riddler admin form.', 'Riddler');
-
-    // This creates a new set of question and response.
-    $ajax = $this->drupalPostAjaxForm(self::RIDDLER_ADMIN_PATH, $form_values_1_question, $addAnotherButton);
-    $this->assertText(t('Riddle 2'),
-      'Admin should be able to ajax add a new riddle row.', 'Riddler');
-
-    $this->drupalPostForm(NULL, $form_values_2_question, 'Save configuration');
-    $this->assertFieldByName('riddler[1][question]', t('What color is Druplicon?'),
-      'Admin should be able to add a new question.', 'Riddler');
-    $this->assertFieldByName('riddler[1][response]', t('blue'),
-      'Admin should be able to add a new response.', 'Riddler');
-
-    // This deletes a set of question and response.
-    $ajax = $this->drupalPostAjaxForm(self::RIDDLER_ADMIN_PATH, $form_values_2_question, 'riddle-remove-1');
-    $this->assertNoFieldByName('riddler[1][question]', NULL,
-      'Admin should be able to ajax remove a new question.', 'Riddler');
-    $this->assertNoFieldByName('riddler[1][response]', NULL,
-      'Admin should be able to ajax remove a new response.', 'Riddler');
-
-    // Save the config form without the deleted riddle.
-    $this->drupalPostForm(NULL, $form_values_1_question, 'Save configuration');
-    $this->assertNoText(t('Riddle 2'),
-      'Admin should be able to save without a deleted riddle.', 'Riddler');
-    $this->assertNoFieldByName('riddler[1][question]', NULL,
-      'Admin should be able to save to remove a new question.', 'Riddler');
-    $this->assertNoFieldByName('riddler[1][response]', NULL,
-      'Admin should be able to save to remove a new response.', 'Riddler');
-
-
-  }
-
-}
diff --git a/tests/src/Functional/RiddlerTestCase.php b/tests/src/Functional/RiddlerTestCase.php
new file mode 100644
index 0000000..6e3b109
--- /dev/null
+++ b/tests/src/Functional/RiddlerTestCase.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace Drupal\Tests\riddler\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+use Drupal\Tests\user\Traits\UserCreationTrait;
+
+/**
+ * Tests Riddler main test case sensitivity.
+ *
+ * @group captcha
+ */
+class RiddlerTestCase extends BrowserTestBase {
+
+  use UserCreationTrait;
+
+  /**
+   * Drupal path of the Riddler admin page.
+   */
+  const RIDDLER_ADMIN_PATH = 'admin/config/people/captcha/riddler';
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['block', 'comment', 'captcha', 'riddler'];
+
+  /**
+   * A test user with administrative privileges.
+   *
+   * @var \Drupal\user\UserInterface
+   */
+  protected $adminUser;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->adminUser = $this->drupalCreateUser(['administer CAPTCHA settings']);
+    $this->drupalLogin($this->adminUser);
+  }
+
+  /**
+   * Method for testing the Riddler riddles administration.
+   */
+  public function testRiddlesAdministration() {
+    $form_values_1_question = [
+      'riddler[0][question]' => 'What is your favorite primary color?',
+      'riddler[0][response]' => 'red, blue, yellow',
+    ];
+    $form_values_2_question = [
+      'riddler[0][question]' => 'What is your favorite primary color?',
+      'riddler[0][response]' => 'red, blue, yellow',
+      'riddler[1][question]' => 'What color is Druplicon?',
+      'riddler[1][response]' => 'blue',
+    ];
+
+    $addAnotherButton = ['op' => 'Add another riddle'];
+
+    // Check that the admin form exists.
+    $this->drupalGet(self::RIDDLER_ADMIN_PATH);
+    $this->assertText(t('Add questions that you require users to answer.'),
+      'Admin should be able to see the Riddler admin form.', 'Riddler');
+
+    // This creates a new set of question and response.
+    $ajax = $this->drupalPostAjaxForm(self::RIDDLER_ADMIN_PATH, $form_values_1_question, $addAnotherButton);
+    $this->assertText(t('Riddle 2'),
+      'Admin should be able to ajax add a new riddle row.', 'Riddler');
+
+    $this->drupalPostForm(NULL, $form_values_2_question, 'Save configuration');
+    $this->assertFieldByName('riddler[1][question]', t('What color is Druplicon?'),
+      'Admin should be able to add a new question.', 'Riddler');
+    $this->assertFieldByName('riddler[1][response]', t('blue'),
+      'Admin should be able to add a new response.', 'Riddler');
+
+    // This deletes a set of question and response.
+    $ajax = $this->drupalPostAjaxForm(self::RIDDLER_ADMIN_PATH, $form_values_2_question, 'riddle-remove-1');
+    $this->assertNoFieldByName('riddler[1][question]', NULL,
+      'Admin should be able to ajax remove a new question.', 'Riddler');
+    $this->assertNoFieldByName('riddler[1][response]', NULL,
+      'Admin should be able to ajax remove a new response.', 'Riddler');
+
+    // Save the config form without the deleted riddle.
+    $this->drupalPostForm(NULL, $form_values_1_question, 'Save configuration');
+    $this->assertNoText(t('Riddle 2'),
+      'Admin should be able to save without a deleted riddle.', 'Riddler');
+    $this->assertNoFieldByName('riddler[1][question]', NULL,
+      'Admin should be able to save to remove a new question.', 'Riddler');
+    $this->assertNoFieldByName('riddler[1][response]', NULL,
+      'Admin should be able to save to remove a new response.', 'Riddler');
+  }
+
+}