Through our main engine, which we call Session Generator, we generate a different series of exercises depending on what we know about a user’s learning needs, settings, platform, and so on. Proofreading a block of curriculum text would be fairly straightforward- but Duolingo is a dynamic app. Learning a language with Duolingo is very different from learning from a textbook or a set curriculum. Limitations of automated testing: Handling nondeterminism It allowed our team to create the course much faster, but it also meant we needed to test every aspect, from content to functionality, that much more thoroughly. Hindi was the first of the Big Five for which we used a new content creation process. While working on Arabic introduced the new challenge of supporting a right-to-left language, it also provided a chance to test improvements in our course deployment process since the Hindi launch. From the launch of Hindi, we learned how to teach and test an alphabet-based and scripted language that is not always clearly delimited by white space.

Our Chinese course launch, for example, forced us to create ways to teach a writing system that’s very different from English and other Latin-script languages. We saved it for last out of the “Big Five” so that we could incrementally tackle new challenges with each new launch. Spoken by over 400 million people worldwide, Arabic has long been on our roadmap, but it came with a unique set of challenges. A primer on text shaping and rendering non-Latin text in the shadow of an ASCII-dominated world.

Chinese in spanish duolingo