Internationalization (I18N) testing is to identify any potential international functionality issues and compare product performance against international requirements prior to global release.
It often also includes pseudo-localization testing (insertion of text that mimics translated content) on the internationalized build to verify the localization-readiness of the product.
This type of testing is a key step in discovering issues that significantly affect the cost of any localization initiative. Some common aspects that require scrutiny for international products include: localized operating system (OS) compliance, character support, locale-dependent behaviors and market dependent requirements and standards.
g11n's I18N Testing will help you ensure the source product has been readied for any target language and market, discover any issues that may have been overlooked, pinpoint areas where modifications are needed. The overall goal is to fix issues early and often and maximize the cost, process and time benefits downstream in the localization process.