$expected_config

array (
  'allowedContent' =>
  array (
    'h4' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
    'h5' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
    'h6' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
    'p' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
    'br' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
    'strong' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
    'a' =>
    array (
      'attributes' => true,
      'styles' => false,
      'classes' => true,
    ),
  ),
  'contentsCss' =>
  array (
    0 => 'http://drupal8.local/core/modules/ckeditor/css/ckeditor-iframe.css',
    1 => 'http://drupal8.local/core/modules/system/css/system.module.css',
  ),
  'customConfig' => '',
  'disallowedContent' =>
  array (
    '*' =>
    array (
      'attributes' => 'on*',
    ),
  ),
  'drupalExternalPlugins' =>
  array (
    'drupalimage' => 'http://drupal8.local/core/modules/ckeditor/js/plugins/drupalimage/plugin.js',
    'drupallink' => 'http://drupal8.local/core/modules/ckeditor/js/plugins/drupallink/plugin.js',
  ),
  'drupalImage_dialogTitleAdd' => 'Insert Image',
  'drupalImage_dialogTitleEdit' => 'Edit Image',
  'drupalLink_dialogTitleAdd' => 'Add Link',
  'drupalLink_dialogTitleEdit' => 'Edit Link',
  'entities' => false,
  'extraPlugins' => 'drupalimage,drupallink',
  'justifyClasses' =>
  array (
    0 => 'text-align-left',
    1 => 'text-align-center',
    2 => 'text-align-right',
    3 => 'text-align-justify',
  ),
  'language' => 'en',
  'pasteFromWordPromptCleanup' => true,
  'resize_dir' => 'vertical',
  'stylesSet' => false,
  'toolbar' =>
  array (
    0 =>
    array (
      'name' => 'Formatting',
      'items' =>
      array (
        0 => 'Bold',
        1 => 'Italic',
      ),
    ),
    1 =>
    array (
      'name' => 'Links',
      'items' =>
      array (
        0 => 'DrupalLink',
        1 => 'DrupalUnlink',
      ),
    ),
    2 =>
    array (
      'name' => 'Lists',
      'items' =>
      array (
        0 => 'BulletedList',
        1 => 'NumberedList',
      ),
    ),
    3 =>
    array (
      'name' => 'Media',
      'items' =>
      array (
        0 => 'Blockquote',
        1 => 'DrupalImage',
      ),
    ),
    4 =>
    array (
      'name' => 'Tools',
      'items' =>
      array (
        0 => 'Source',
      ),
    ),
    5 => '/',
  ),
)