Issue #3225738 by TR: Add test case for settings form

tests/src/Functional/RegcodeSettingsTest.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\Tests\regcode\Functional;
+
+use Drupal\Tests\BrowserTestBase;
+
+// cspell:ignore unpriv
+
+/**
+ * Tests operation of the Regcode settings page.
+ *
+ * @group Regcode
+ */
+class RegcodeSettingsTest extends BrowserTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = ['regcode', 'help', 'block'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $defaultTheme = 'stark';
+
+  /**
+   * Admin user.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $adminUser;
+
+  /**
+   * Authenticated but unprivileged user.
+   *
+   * @var \Drupal\Core\Session\AccountInterface
+   */
+  protected $unprivUser;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp(): void {
+    parent::setUp();
+
+    // System help block is needed to see output from hook_help().
+    $this->drupalPlaceBlock('help_block', ['region' => 'help']);
+
+    // Create our test users.
+    $this->adminUser = $this->createUser([
+      'administer site configuration',
+      'access administration pages',
+      'administer registration codes',
+    ]);
+    $this->unprivUser = $this->createUser();
+  }
+
+  /**
+   * Tests module permissions / access to configuration page.
+   */
+  public function testUserAccess() {
+    /** @var \Drupal\Tests\WebAssert $assert */
+    $assert = $this->assertSession();
+
+    // Test as anonymous user.
+    $this->drupalGet('admin/config/people/regcode/settings');
+    $assert->statusCodeEquals(403);
+    $assert->pageTextContains('Access denied');
+    $assert->pageTextContains('You are not authorized to access this page.');
+
+    // Test as authenticated but unprivileged user.
+    $this->drupalLogin($this->unprivUser);
+    $this->drupalGet('admin/config/people/regcode/settings');
+    $assert->statusCodeEquals(403);
+    $this->drupalLogout();
+
+    // Test as admin user.
+    $this->drupalLogin($this->adminUser);
+    $this->drupalGet('admin/config/people/regcode/settings');
+    $assert->statusCodeEquals(200);
+    $assert->pageTextContains('Configure the registration code module.');
+    $this->drupalLogout();
+  }
+
+}