Why does simpletest report a missing schema for my Drupal 8 module? My module is working as expected with the following settings, config and config export. But when I try to run tests, I get the following error. I'm not sure what is wrong. 


  Drupal\Core\Config\Schema\SchemaIncompleteException: Schema errors for riddler.settings with the following errors: riddler.settings:riddles missing schema in Drupal\Core\Config\Testing\ConfigSchemaChecker->onConfigSave() (line 102 of /var/www/sb/sboss/docroot/core/lib/Drupal/Core/Config/Testing/ConfigSchemaChecker.php).


# settings.yml
riddles:
 -
    question: 'Do you really hate Spam?'
    response: 'Yes!'
langcode: en


--------------------------------


#schema
riddler.settings:
  type: config_object
  riddles:
      question:
        type: label
        label: 'Question'
      response:
        type: label
        label: 'Response'


#config export

riddles:
 -
    question: 'Do you really hate Spam?'
    response: Yes!
  -
    question: 'What''s your favorite primary color?'
    response: 'blue, yellow, red'
I see several errors, not sure which one trips you: you missed a type for riddles and tried to define a mapping immediately under. But riddles is a sequence and each element in the sequence is that mapping. So:

riddler.settings:
  type: config_object
  mapping:
    riddles:
      type: sequence
      sequence:
        type: mapping
          question:
            type: label
            label: 'Question'
          response:
            type: label
            label: 'Response'


At least that's what I would attempt...