Impact analysis on subclass

Question

I was modifying an overridden method of a subclass. In order to determine the impact of the change, I went through all possible scenarios and tested them.

The problem is, the "all possible scenarios" are determined by reading business use cases, putting break point to find out when this particular overridden method is being hit instead of others.

Is there a reliable or programmatic way to find out about impacts? For example, if it is not an overridden method, I can simply "Find All Instance" or even using grep to find where it is getting called. Is there a similar measure for overridden methods? Or is it just an inconvenience of polymorphism?

Answer 1

A quick suggestion would be to rename the function. The compiler will let you know quickly about what needs to be looked at and possibly refactored. Obviously this entirely depends upon you being in control of all possible client code.

Answer 2

There may be scientific approaches to this topic. But in general you will likely have to go with the "just an inconvenience of polymorphism".

I know there are people how outright oppose any OO for this very reason. In fact this was also the reason why in .Net methods are, unlike in Java, by default NOT overridable.

If you search on google for polymorphism breaks encapsulation or inheritance breaks encapsulation you will find lots of discussions on that topic.

Answer 3

I don't know all the details so it's hard to speculate, but what impact do you expect the change to have?

So long as you aren't changing the method's signature, just verify the behavior of the class in isolation. This is a key principle of unit testing. Since you mention breakpoints, I'm assuming that you're testing manually in the debugger. Unit testing can get you away from all that; it's worth looking into.

If the method modifies global state or if the class is tightly coupled to other classes, testing in isolation may be difficult. See Adding unit tests to legacy code.

As another option, ReSharper has a Find Usages feature that can find callers of a method and optionally callers of the base class. There's also an option to find overriding methods under Find Usages Advanced.