JUnit testing to get the bigger number of 2 values?

JUnit testing to get the bigger number of 2 values?

I need some help figuring out how to get a JUnit test of the bigger number
of 2 values.
I know how to do Junit testing of simple functions like adding,
subtracting and etc but not finding a bigger value of the two.
This is what I have:
public static int getMax(int x, int y){
if(x >= y) {
return x;
}
else {
return y;
}
}
Im stuck on proving what I wrote.