Refactor \Drupal\eck\Entity\EckEntity::baseFieldDefinitions to use the parent method

+++ b/src/Entity/EckEntity.php
@@ -80,39 +80,16 @@ class EckEntity extends ContentEntityBase implements EckEntityInterface {
+  public static function baseFieldDefinitions(EntityTypeInterface $entityType) {
+    $fields = parent::baseFieldDefinitions($entityType);

That's a change which is unrelated IMHO. Feel free to do so though. I'm a huge fan of optimizing for reviewablity, aka. change one thing at a time.

+++ b/tests/src/Unit/UnitTestBase.php
@@ -1,135 +1,155 @@
+namespace Drupal\eck\Entity {
+  if (!function_exists('t')) {
+    function t($string) {
+      return $string;
+    }
+  }
 }

note: on the longrun you can use TranslatableMarkup::create(), out of scope of this issue of course.