Update to Drupal 8.1.5. For more information, see https://www.drupal.org/project/drupal/releases/8.1.5

core/modules/system/tests/modules/entity_test/src/Entity/EntityTestMultiValueBasefield.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace Drupal\entity_test\Entity;
+
+use Drupal\Core\Entity\EntityTypeInterface;
+
+/**
+ * Defines an entity type with a multivalue base field.
+ *
+ * @ContentEntityType(
+ *   id = "entity_test_multivalue_basefield",
+ *   label = @Translation("Entity Test with a multivalue base field"),
+ *   base_table = "entity_test_multivalue_basefield",
+ *   data_table = "entity_test_multivalue_basefield_field_data",
+ *   handlers = {
+ *     "views_data" = "Drupal\views\EntityViewsData",
+ *   },
+ *   entity_keys = {
+ *     "id" = "id",
+ *     "uuid" = "uuid",
+ *     "bundle" = "type",
+ *     "label" = "name",
+ *     "langcode" = "langcode",
+ *   }
+ * )
+ */
+class EntityTestMultiValueBasefield extends EntityTest {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function baseFieldDefinitions(EntityTypeInterface $entity_type) {
+    $fields = parent::baseFieldDefinitions($entity_type);
+    $fields['name']->setCardinality(2);
+
+    return $fields;
+  }
+
+}