isI18NBackendDefault() public method

(if false: backend unset/there's an error)
 /**
  * Test SimpleSAML\Locale\Localization().
  */
 public function testLocalization()
 {
     // The constructor should activate the default domain
     $c = \SimpleSAML_Configuration::loadFromArray(array('language.i18n.backend' => 'SimpleSAMLphp'));
     $l = new Localization($c);
     $this->assertTrue($l->isI18NBackendDefault());
     $this->assertEquals(Localization::DEFAULT_DOMAIN, 'messages');
 }