Localization testing checks appropriate linguistic and cultural aspects for a particular location - including change in the user interface or any other settings according to the demands or requirements.
This process includes utilizing many different testers to repeat the same functions. They help verify various factors like cultural appropriateness of UI, typographical errors, linguistic errors, etc.
At Word Publishing, we perform linguistic testing using professionals who extract screen grabs from the localized application. These are then proofread by professional native linguists. We adopt this approach as it is cost-effective to linguistic testing.
Localization testing is validating that the application performs functionally in localized applications. This is a different process than linguistic testing but can be performed simultaneously.
It is usually not feasible, nor needed, to do full linguistic and localization testing across all languages or products. At Word Publishing, we work closely with our customers to devise a testing strategy based on their requirements.