  We describe how we both use and extend the PrarieLearn framework by taking
advantage of its built-in support for external auto-graders. By using a custom
Docker container, we can match our course requirements perfectly. Moreover, by
relying on the flexibility of the interface we can customize our Docker
container. A specific extension for unit testing is described which creates
context-dependent difference between student answers and reference solution
providing a more comprehensive response at test time.
