contribution in kernel community & testing kernel

Hi, I a novice & want to contribute to linux community. I have basic knowledge of kernel. Problem statement: I want to work on x86 architecture. I am not sure how to go about unit testing. I can use qemu for testing but i find kernel on x86 architecture too big to compile. How i can get the smaller size kernel on x86 architecture? Please help me setting up testing environment so that i can test my changes properly & quickly. thanks, Shubham