diff --git a/core/modules/migrate/src/Plugin/migrate/process/Migration.php b/core/modules/migrate/src/Plugin/migrate/process/Migration.php
index 24ce411..1b4160a 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/Migration.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/Migration.php
@@ -2,8 +2,8 @@
 
 namespace Drupal\migrate\Plugin\migrate\process;
 
-@trigger_error('The '. __NAMESPACE__ . '\Migration is deprecated in
-Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, use '. __NAMESPACE__ . '\MigrationLookup', E_USER_DEPRECATED);
+@trigger_error('The ' . __NAMESPACE__ . '\Migration is deprecated in
+Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, use ' . __NAMESPACE__ . '\MigrationLookup', E_USER_DEPRECATED);
 
 /**
  * Calculates the value of a property based on a previous migration.
diff --git a/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php b/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php
index d768443..2b4d8b6 100644
--- a/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php
+++ b/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\migrate\Unit\process;
 
 use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\migrate\MigrateSkipProcessException;
 use Drupal\migrate\Plugin\MigrationInterface;
 use Drupal\migrate\Plugin\migrate\process\MigrationLookup;
 use Drupal\migrate\Plugin\MigrateDestinationInterface;
@@ -102,6 +103,7 @@ public function testSkipOnEmpty() {
     ];
     $migration_plugin->id()->willReturn(uniqid());
     $migration = new MigrationLookup($configuration, 'migration_lookup', [], $migration_plugin->reveal(), $migration_plugin_manager->reveal(), $process_plugin_manager->reveal());
+    $this->setExpectedException(MigrateSkipProcessException::class);
     $migration->transform(0, $this->migrateExecutable, $this->row, 'foo');
   }
 
diff --git a/core/modules/migrate/tests/src/Unit/process/MigrationTest.php b/core/modules/migrate/tests/src/Unit/process/MigrationTest.php
index c8d6a02..843d1e5 100644
--- a/core/modules/migrate/tests/src/Unit/process/MigrationTest.php
+++ b/core/modules/migrate/tests/src/Unit/process/MigrationTest.php
@@ -2,8 +2,8 @@
 
 namespace Drupal\Tests\migrate\Unit\process;
 
-@trigger_error('The '. __NAMESPACE__ . '\MigrationTest is deprecated in
-Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, use '. __NAMESPACE__ . '\MigrationLookupTest', E_USER_DEPRECATED);
+@trigger_error('The ' . __NAMESPACE__ . '\MigrationTest is deprecated in
+Drupal 8.4.0 and will be removed before Drupal 9.0.0. Instead, use ' . __NAMESPACE__ . '\MigrationLookupTest', E_USER_DEPRECATED);
 
 use Drupal\Core\Entity\EntityStorageInterface;
 use Drupal\migrate\MigrateSkipProcessException;