如何验证重构保留了代码流，而不仅仅是行为?

Sometimes, I see if-statements that could be written in a better way. Usually these are cases where we have several layers of nested if-statements and I've identified a simpler way of rewriting the block of if-statements. Of course the biggest concern is that the resulting code will have a different code flow in certain cases. Sometimes, I see if-statements that could be wr