There is a library called reagent which is a wrapper for React, check it out: https://reagent-project.github.io/

It uses a the same data format as hiccup template library which can be used on server side - https://github.com/weavejester/hiccup

That's why the same code can be used on client and server. The simplicity of the process (uses pure functions to turn immutable data structures to html) means that it can be also easily unit tested.