reverted:
--- b/core/modules/migrate_drupal/tests/src/Unit/source/d6/Drupal6SqlBaseTest.php
+++ a/core/modules/migrate_drupal/tests/src/Unit/source/d6/Drupal6SqlBaseTest.php
@@ -80,8 +80,6 @@
     // Should be 1 theme and 2 modules.
     $this->assertEquals(1, count($system_data['theme']));
     $this->assertEquals(2, count($system_data['module']));
-    $this->assertIdentical(1, count($system_data['theme']));
-    $this->assertIdentical(2, count($system_data['module']));
 
     // Calling again should be identical.
     $this->assertSame($system_data, $this->base->getSystemData());