Localization testing is essential when your web app serves users from multiple languages. To effectively conduct localization testing for multiple-lingual web apps, several steps should be taken.
First and foremost, an application should support localization with language packs or resource files which can be tested to ensure accurate and consistent translations across languages. Furthermore, its user interface and layout should also be rigorously scrutinized against various character sets and formats of different languages to ensure compatibility.
Furthermore, testing should cover scenarios like date/time formats, currency symbols, and regional variations.