Open-source software with UML diagrams documented in order to test my app

So, I am working on my final paper for my Computer Science degree. I prototyped a method that automatically creates unit tests for a given software based on its UML diagrams, specifically Sequence Diagrams: It reads the diagram and generates junits.

Now I am on the phase of testing my prototype with a real software. I would like some suggestions on Open-source softwares with the corresponding UML Diagrams documented.

I can´t seem to find on Google a software with the diagrams, so I would have to make them all myself just to test my app...

Any ideas are of great help! Thanks!