For several new features we are currently making quite extensive changes to FIMK core.
Right now mainly for the private assets feature but some other big implementations are around the corner.
To make sure this all works properly tests are required that can simulate a working blockchain.
We've had the Java based Junit tests for some time now but the main recurring problem was all the code you'd have to write to make a simple test.
This had to be done easier. Writing tests should be quick and fun, only then will you write tests that touch all parts of the software. And having an easy to use testing tool allows for much faster development.
Hopefully soon we'll have more people writing tests which leads to a better code base and allows other developers to get started quicker with FIMK core development.