reverted:
--- b/core/tests/Drupal/FunctionalJavascriptTests/EntityReference/EntityReferenceAutocompleteWidgetTest.php
+++ a/core/tests/Drupal/FunctionalJavascriptTests/EntityReference/EntityReferenceAutocompleteWidgetTest.php
@@ -88,7 +88,7 @@
     $page = $this->getSession()->getPage();
 
     $autocomplete_field = $page->findField($field_name . '[0][target_id]');
+    $autocomplete_field->setValue('Test');
-    $autocomplete_field->setValue('Test page');
     $this->getSession()->getDriver()->keyDown($autocomplete_field->getXpath(), ' ');
     $assert_session->waitOnAutocomplete();