+
+ // If prefix negotiation is used, make sure that no domains are migrated.
+ // Otherwise there will be validation errors when trying to save URL
+ // language detection configuration from the UI.
+ $expected_domains = [
+ 'en' => '',
+ 'fr' => '',
+ 'is' => '',
+ ];
+ $this->assertSame($expected_domains, $config->get('url.domains'));