(1) If some classes are co-changed again and again, without refactoring, what kind of tool/strategy do you usually use to guarantee that you don't commit error of omission? For instance, writing some scripts, memorize the correlated classes and leverage your expertise when debugging, etc.?

(2) For the method pairs which are pain points, how do you decide whether the gain is greater than pain by applying refactoring? How much difference or what kind of difference will your extracted method allow? Different variable names, method calls, used types?

Will you try to use some really complicated refactorings in order to avoid the error of omission mentioned above, such as Delegate design pattern, Parameterize Type (declare a template with type parameters to define an extracted method which works on differently typed variables)? Will you also reconstruct the code if two code snippets are syntactically different but semantically equivalent?