--- /dev/null
+<?php
+
+/**
+ * @file
+ * Test fixture.
+ */
+
+use Drupal\Core\Database\Database;
+
+$connection = Database::getConnection();
+
+// Add a layout plugin to an existing entity view display without explicitly
+// enabling Layout Builder for this display.
+$display = $connection->select('config')
+ ->fields('config', ['data'])
+ ->condition('collection', '')
+ ->condition('name', 'core.entity_view_display.block_content.basic.default')
+ ->execute()
+ ->fetchField();
+$display = unserialize($display);
+$display['third_party_settings']['layout_builder']['sections'][] = [
+ 'layout_id' => 'layout_onecol',
+ 'layout_settings' => [],
+ 'components' => [
+ 'some-uuid' => [
+ 'uuid' => 'some-uuid',
+ 'region' => 'content',
+ 'configuration' => [
+ 'id' => 'system_powered_by_block',
+ ],
+ 'additional' => [],
+ 'weight' => 0,
+ ],
+ ],
+];
+$connection->update('config')
+ ->fields([
+ 'data' => serialize($display),
+ 'collection' => '',
+ 'name' => 'core.entity_view_display.block_content.basic.default',
+ ])
+ ->condition('collection', '')
+ ->condition('name', 'core.entity_view_display.block_content.basic.default')
+ ->execute();