ISTWCMS-4182: Test codepen embed block

tests/src/Functional/UwWcmsBasicTest.php

@@ -719,7 +719,8 @@ class UwWcmsBasicTest extends BrowserTestBase {
           // Create CodePen block.
           $edit = [
             'edit-settings-label' => $this->randomString(),
-            'edit-settings-block-form-field-codepen-id-0-value' => $this->randomMachineName(7),
+            // Letters only, 6-7 characters.
+            'edit-settings-block-form-field-codepen-id-0-value' => substr(preg_replace('/[^a-zA-Z]+/', '', $this->randomMachineName(24)), 0, 7),
             'edit-settings-block-form-field-codepen-username-0-value' => $this->randomMachineName(),
             'edit-settings-block-form-field-codepen-displayed-author-0-value' => $this->randomString(),
             'edit-settings-block-form-field-codepen-displayed-title-0-value' => $this->randomString(),