diff -u b/core/modules/migrate_drupal_ui/src/Tests/MigrateUpgradeTestBase.php b/core/modules/migrate_drupal_ui/src/Tests/MigrateUpgradeTestBase.php
--- b/core/modules/migrate_drupal_ui/src/Tests/MigrateUpgradeTestBase.php
+++ b/core/modules/migrate_drupal_ui/src/Tests/MigrateUpgradeTestBase.php
@@ -173,6 +173,8 @@
     $this->assertNoText(t('Source module not found for module_no_annotation.'));
     $this->assertNoText(t('Source module not found for modules_available_test.'));
     $this->assertNoText(t('Destination module not found for modules_available_test'));
+    // Check for any missing module errors.
+    $this->assertNoText(t('module not found'));
     $this->drupalPostForm(NULL, [], t('Perform upgrade'));
     $this->assertText(t('Congratulations, you upgraded Drupal!'));