Issue #2057199 by lauriii, olli: Unable to select the 'Default' view mode for custom block.

core/modules/block/custom_block/lib/Drupal/custom_block/Plugin/Block/CustomBlockBlock.php

@@ -92,7 +92,7 @@ public function defaultConfiguration() {
    * Adds body and description fields to the block configuration form.
    */
   public function blockForm($form, &$form_state) {
-    $options = array();
+    $options = array('default' => t('Default'));
     $view_modes = entity_get_view_modes('custom_block');
     foreach ($view_modes as $view_mode => $detail) {
       $options[$view_mode] = $detail['label'];

core/modules/block/custom_block/lib/Drupal/custom_block/Tests/CustomBlockCreationTest.php

@@ -78,6 +78,10 @@ public function testCustomBlockCreation() {
     $this->drupalGet('admin/structure/block/manage/testblock');
     $this->assertFieldByXPath('//select[@name="settings[custom_block][view_mode]"]/option[@selected="selected"]/@value', 'test_view_mode', 'View mode changed to Test View Mode');
 
+    // Test the available view mode options.
+    $this->assertOption('edit-settings-custom-block-view-mode', 'default', 'The default view mode is available.');
+    $this->assertOption('edit-settings-custom-block-view-mode', 'full', 'The full view mode is available.');
+
     // Check that the block exists in the database.
     $blocks = entity_load_multiple_by_properties('custom_block', array('info' => $edit['info']));
     $block = reset($blocks);