打破类中所有依赖项的最简单，最快捷的方法

Question

When working with legacy code, and trying to create tests, I often break out dependencies from classes or methods so I can write unit tests using mocks for these dependencies. Dependencies most often come in the form of calls to static classes and objects created using the new keyword in the constructor or other locations in that class.

In most cases, static calls are handled either by wrapping the static dependency, or if its a singleton pattern (or similar) in the form of StaticClass.Current.MethodCall() passing that dependency by its interface go the constructor instead.

In most cases, uses of the new keyword in the constructor is simply replaced by passing that interface in the constructor instead.

In most cases, uses of the new keyword in other parts of the class, is handled either by the same method as above, or by if needed create a factory, and pass the factory's interface in the constructor.

I always use Resharpers refactoring tools to help me all of these break-outs, however most things are still manual labour (which could be automated), and for some legacy classes and methods that can be a very very tedious process. Is there any other refactoring plugins and/or tools which would help me in this process? Is there a "break out all depencencies from this class in a single click" refactoring tool? =)

It sounds to me like all these steps are common for many developers and a common problem, and before I attempt writing plugin to Resharper or CodeRush, I have to ask, because someone has probably already attempted this..

ADDED:

In reflection to answers below: even if you might not want to break out everything at once (one click total break out might cause more problems than it helps) still being able to simply break out 1 methods dependencies, or 1-2 dependencies easily, would be of big difference.

Also, refactoring code has a measure of "try and see what happens just to learn how everything fits together", and a one click total break out would help that process tons, even if you dont check that code in..

Answer 1

I don't think there is any tool that can automate this for you. Working with legacy code means -as you know- changing code with little steps at a time. The steps are often deliberately small to prevent errors from being made. Usually the first change you should make is one that makes that code testable. After you've written the test you change that part of the code in such way that you fix the bug or implement the RFC.

Because you should take small steps I believe it is hard to use a refactoring tool to magically make all your dependencies disappear. With legacy systems you would hardly ever want to make big changes at once, because the risk of breaking (and not finding out because of the lack of tests) is too big. This however, doesn't mean refactoring tools aren't useful in this scenario. On the contrary; they help a lot.

If you haven't already, I'd advise you to read Michael Feathers' book Working Effectively with Legacy Code . It describes in great details a series of patterns that help you refactor legacy code to a more testable system.

Good luck.

Answer 2

When it comes to static call dependencies, you might want to check out Moles . It's able to do code injection at run-time to stub out any static or non-virtual method call with your own test implementation. This is handy for testing legacy code that wasn't designed using testable dependency-injected interfaces.