How do I populate the fields of a complex recusive class randomly in C#

So I want to do some automated tests that check for certain errors (key not found, null pointer, other unhandled exceptions) and to do so I have decided to give fuzzing a go.

Now the class I want to test is complexly nested contains several arrays (even several layers deep etc.) and I would like to fuzz this entire structure, unfortunately the complexity makes it impractical to write a random generator for every variable (including several recursions deep). The entire thing is however serializable if that helps.

I have found this fuzzing lib, however that seems to require a schema which this class structure is I think to complex to manually craft.