diff --git a/core/modules/migrate/tests/src/Unit/process/MigrationTest.php b/core/modules/migrate/tests/src/Unit/process/MigrationTest.php
index dfac1c9..5bcbd43 100644
--- a/core/modules/migrate/tests/src/Unit/process/MigrationTest.php
+++ b/core/modules/migrate/tests/src/Unit/process/MigrationTest.php
@@ -199,4 +199,46 @@ public function successfulLookupDataProvider() {
     ];
   }
 
+  /**
+   * Tests processing multiple source IDs.
+   */
+  public function testMultipleSourceIds() {
+    $migration_plugin = $this->prophesize(MigrationInterface::class);
+    $migration_plugin_manager = $this->prophesize(MigrationPluginManagerInterface::class);
+    $process_plugin_manager = $this->prophesize(MigratePluginManager::class);
+    $foobaz_migration = $this->prophesize(MigrationInterface::class);
+    $get_migration = $this->prophesize(Migration::class);
+    $id_map = $this->prophesize(MigrateIdMapInterface::class);
+    $destination_plugin = $this->prophesize(MigrateDestinationInterface::class);
+    $source_plugin = $this->prophesize(MigrateSourceInterface::class);
+
+    $migration_plugin_manager->createInstances(['foobaz'])
+      ->willReturn(['foobaz' => $foobaz_migration->reveal()]);
+
+    $process_plugin_manager->createInstance('get', ['source' => ['blog_id', 'cat_id']], $migration_plugin->reveal())
+      ->willReturn($get_migration->reveal());
+
+    $foobaz_migration->getIdMap()->willReturn($id_map->reveal());
+    $foobaz_migration->getDestinationPlugin(TRUE)->willReturn($destination_plugin->reveal());
+    $foobaz_migration->getProcess()->willReturn([]);
+    $foobaz_migration->getSourcePlugin()->willReturn($source_plugin->reveal());
+    $foobaz_migration->id()->willReturn('foobaz');
+    $foobaz_migration->getSourceConfiguration()->willReturn([]);
+
+    $get_migration->transform(NULL, Argument::any(), Argument::any(), Argument::any())
+      ->willReturn(['blog_id_eg', 99]);
+
+    $destination_plugin->import(Argument::any())->willReturn([2]);
+
+    $source_plugin->getIds()->willReturn(['blog_id' => [], 'cat_id' => []]);
+
+    $configuration = [
+      'migration' => 'foobaz',
+      'source_ids' => ['foobaz' => ['blog_id', 'cat_id']],
+    ];
+    $migration = new Migration($configuration, 'migration', [], $migration_plugin->reveal(), $migration_plugin_manager->reveal(), $process_plugin_manager->reveal());
+    $result = $migration->transform(1, $this->migrateExecutable, $this->row, 'foo');
+    $this->assertEquals(2, $result);
+  }
+
 }