There were 2 errors:
1) Drupal\Tests\tagify\FunctionalJavascript\FieldWidget\TagifyEntityReferenceAutocompleteWidgetTest::testSingleValueWidget with data set #0 ('CONTAINS', true)
RuntimeException: Unable to complete AJAX request.
/var/www/html/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php:117
/var/www/html/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php:38
/var/www/html/modules/contrib/tagify/tests/src/FunctionalJavascript/FieldWidget/TagifyEntityReferenceAutocompleteWidgetTest.php:62
/var/www/html/vendor/phpunit/phpunit/src/Framework/TestResult.php:728
2) Drupal\Tests\tagify\FunctionalJavascript\FieldWidget\TagifyEntityReferenceAutocompleteWidgetTest::testSingleValueWidget with data set #1 ('STARTS_WITH', true)
RuntimeException: Unable to complete AJAX request.
/var/www/html/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php:117
/var/www/html/core/tests/Drupal/FunctionalJavascriptTests/JSWebAssert.php:38
/var/www/html/modules/contrib/tagify/tests/src/FunctionalJavascript/FieldWidget/TagifyEntityReferenceAutocompleteWidgetTest.php:62
/var/www/html/vendor/phpunit/phpunit/src/Framework/TestResult.php:728
ERRORS!
Tests: 2, Assertions: 14, Errors: 2.
HTML output was generated
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-1-84252840.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-2-84252840.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-3-84252840.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-4-84252840.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-5-84252840.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-6-81517671.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-7-81517671.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-8-81517671.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-9-81517671.html
http://php-apache-jenkins-drupal-contrib-770086/subdirectory/sites/simpletest/browser_output/Drupal_Tests_tagify_FunctionalJavascript_FieldWidget_TagifyEntityReferenceAutocompleteWidgetTest-10-81517671.htmlFixed
1.2
Code