Develop Reference

Use virtual protected factory methods to mock objects created within a class?

Rhino Mocks is tightly coupled with the design pattern of using dependency injection and constructor injection, but I typically don't follow the dependency-injection paradigm and don't like to re-architect my solution just for my test tool.
Take this scenario:
class MyClass{
public void MyMethod(...){
var x = new Something(...);
x.A();
x.B();
x.C();
}
}
Would it be quite typical and acceptable to instead do the following, since this is not a case where I would generally wish to inject the dependency - it can be considered part of MyClass' behaviour/logic.
class MyClass{
public void MyMethod(...){
var x = NewSomething(...);
x.A();
x.B();
x.C();
}
virtual protected Something NewSomething(...){
return new Something(...);
}
}
Now I can (I think) extend MyClass either as a concrete class in my test project, or using Rhino... right? Is this a)correct b)a reasonably sensible, commonplace way of doing things?
Another approach I can see other than DI could be that I actually have a ClassFactory class in my project which creates all instances as needed; then I find a way to mock/stub that in my tests. But this seems 'smelly' to me, though I'm aware it is a pattern some people use.

I have used this quite a few times when trying to make legacy code more testable, although it really likes to come back and bite you later.
Basically, mocks/fakes/testdoubles are your enemy. You should hate them and avoid them (Edit note: I'm not saying don't use them, I'm saying use them only when you HAVE to). It all follows from the paradigm that all code is bad code, and we should write as little code as necessary to complete the task. Having a bunch of test doubles overriding virtual methods makes your code very rigid. It makes it really painful to change a method signature, even if your production code only invokes the method in a single place, because your test doubles will also break. It also makes it painful to later on clean up the mess and actually inject the dependency (and yes, I would argue injecting stuff is Objectively Better(tm)).
What it comes down to is basically: Yes, doing this will make your code more testable, but without any of the benefits you usually get by testing. You wn't get better design, you'll have rigid code etc.
I won't really point any fingers though, since I like I said have used this on occasion just to get a test up to see if something works. It can be a temporary solution that is "good enough", but my final answer is "probably don't if you can at all avoid it (and still have tested code)".

You would be sacrificing the Single Responsability Pattern (SRP) with the method that you're suggesting, and arguably making your code harder to read, understand and maintain, there's a smell right there, before we even reach the talking about tests.
If you plan to run tests, and at the same time not follow SOLID principles , then where are you saving on time, readability, or agility? (I honestly would love to know).
What the DI principle allows you to do is to run your tests completely in isolation from your dependencies, which is exactly what you want to be doing.
The SOLID principles of OOP have many good arguments going for them, but I'm always open to learn and be wrong, but I must say, I may have been blinded by several years of SOLID code, and tens of thousands of green unit tests securing my projects.

How to use unit tests in projects with many levels of indirection

I was looking over a fairly modern project created with a big emphasis on unit testing. In accordance with old adage "every problem in object oriented programming can be solved by introducing new layer of indirection" this project was sporting multiple layers of indirection. The side-effect was that fair amount of code looked like following:
public bool IsOverdraft)
{
balanceProvider.IsOverdraft();
}
Now, because of the empahsis on unit testing and maintaining high code coverage, every piece of code had unit tests written against it.Therefore this little method would have three unit tests present. Those would check:
If balanceProvider.IsOverdraft() returns true then IsOverdraft should return true
If balanceProvider.IsOverdraft() returns false then IsOverdraft should return false
If balanceProvider throws an exception then IsOverdraft should rethrow the same exception
To make things worse, the mocking framework used (NMock2) accepted method names as string literals, as follows:
NMock2.Expect.Once.On(mockBalanceProvider)
.Method("IsOverdraft")
.Will(NMock2.Return.Value(false));
That obviously made "red, green, refactor" rule into "red, green, refactor, rename in test, rename in test, rename in test". Using differnt mocking framework like Moq, would help with refactoring, but it would require a sweep trough all existing unit tests.
What is the ideal way to handle this situation?
A) Keep smaller levels of layers, so that those forwarding calls do not happen anymore.
B) Do not test those forwarding methods, as they do not contain business logic. For purposes of coverage marked them all with ExcludeFromCodeCoverage attribute.
C) Test only if proper method is invoked, without checking return values, exceptions, etc.
D) Suck it up, and keep writing those tests ;)

Either B or C. That's the problem with such general requirements ("every method must have unit test, every line of code needs to be covered") - sometimes, benefit they provide is not worth the cost. If it's something you came up with, I suggest rethinking this approach. The "we must have 95% code coverage" might be appealing on paper but in practice it quickly spawns problems like the one you have.
Also, the code you're testing is something I'd call trivial code. Having 3 tests for it is most likely overkill. For that single line of code, you'll have to maintain like 40 more. Unless your software is mission critical (which might explain high-coverage requirement), I'd skip those tests.
One of the (IMHO) most pragmatic advices on this topic was provided by Kent Beck some time ago on this very site and I expanded a bit on those thoughts with in my blog posts - What should you test?

Honestly, I think we should write tests only to document our code in an helpful manner. We should not write tests just for the sake of code coverage. (Code coverage is just a great tool to figure out what it is NOT covered so that we can figure out if we did forget important unit tests cases or if we actually have some dead code somewhere).
If I write a test, but the test ends up just being a "duplication" of the implementation or worse...if it's harder to understand the test than the actual implementation....then really such a test should not exists. Nobody is interested in reading such tests. Tests should not contain implementation details. Test are about "what" should happen not "how" it will be done. Since you've tagged your question with "TDD", I would add that TDD is a design practice. So if I already know 100% sure in advance what will be the design of what i'm going to implement, then there is no point for me to use TDD and write unit tests (But I will always have in all cases a high level acceptance test that will cover that code). That will happen often when the thing to design is really simple, like in your example. TDD is not about testing and code coverage, but really about helping us to design our code and document our code. There is no point to use a design tool or a documentation tool for designing/documenting simple/obvious things.
In your example, it's far easier to understand what's going on by reading directly the implementation than the test. The test doesn't add any value in term of documentation. So I'd happily erase it.
On top of that such tests are horridly brittle, because they are tightly coupled to the implementation. That's a nightmare on the long term when you need to refactor stuff since any time you will want to change the implementation they will break.
What I'd suggest to do, is to not write such tests but instead have higher level component tests or fast integration tests/acceptance tests that would exercise these layers without knowing anything at all about the inner working.

I think one of the most important things to keep in mind with unit tests is that it doesn't necessarily matter how the code is implemented today, but rather what happens when the tested code, direct or indirect, is modified in the future.
If you ignore those methods today and they are critical to your application's operation, then someone decides to implement a new balanceProvider at some point down the road or decides that the redirection no longer makes sense, you will most likely have a failure point.
So, if this were my application, I would first look to reduce the forward-only calls to a bare minimum (reducing the code complexity), then introduce a mocking framework that does not rely on string values for method names.

A couple of things to add to the discussion here.
Switch to a better mocking framework immediately and incrementally. We switched from RhinoMock to Moq about 3 years ago. All new tests used Moq, and often when we change a test class we switch it over. But areas of the code that haven't changed much or have huge test casses are still using RhinoMock and that is OK. The code we work with from day to day is much better as a result of making the switch. All test changes can happen in this incremental way.
You are writing too many tests. An important thing to keep in mind in TDD is that you should only write code to satisfy a red test, and you should only write a test to specify some unwritten code. So in your example, three tests is overkill, because at most two are needed to force you to write all of that production code. The exception test does not make you write any new code, so there is no need to write it. I would probably only write this test:
[Test]
public void IsOverdraftDelegatesToBalanceProvider()
{
var result = RandomBool();
providerMock.Setup(p=>p.IsOverdraft()).Returns(result);
Assert.That(myObject.IsOverDraft(), Is.EqualTo(result);
}
Don't create useless layers of indirection. Mostly, unit tests will tell you if you need indirection. Most indirection needs can be solved by the dependency inversion principle, or "couple to abstractions, not concretions". Some layers are needed for other reasons (I make WCF ServiceContract implementations a thin pass through layer. I also don't test that pass through). If you see a useless layer of indirection, 1) make sure it really is useless, then 2) delete it. Code clutter has a huge cost over time. Resharper makes this ridiculously easy and safe.
Also, for meaningful delegation or delegation scenarios you can't get rid of but need to test, something like this makes it a lot easier.

I'd say D) Suck it up, and keep writing those tests ;) and try to see if you can replace NMock with MOQ.
It might not seem necessary and even though it's just delegation now, but the tests are testing that it's calling the right method with right parameters, and the method itself is not doing anything funky before returning values. So it's a good idea to cover them in tests. But to make it easier use MOQ or similiar framework that'll make it so much easier to refactor.

Testing Classes - When to refactor?

I'm writing a series of automatic tests in C# using NUnit and Selenium.
Edit: I am testing an entire website, to begin I wrote three classes for the three types of members that use the website, these classes contain methods which use selenium to perform various actions by these members. These classes are then created and their methods called by my test classes with the appropriate inputs.
My question is:
Does it matter how large my test class becomes? (i.e. thousands of tests?)
When is it time to refactor my functionality classes? (25 or 50 methods, 1000 lines of code, etc)
I've been trying to read all I can about test design so if you have any good resources I would appreciate links.

Does it matter how large my test class becomes? (i.e. thousands of tests?)
Yes it does. Tests need to be maintained in the long term, and a huge test class is difficult to understand and maintain.
When is it time to refactor my functionality classes? (25 or 50 methods, 1000 lines of code, etc)
When you start to feel it is awkward to find a specific test case, or to browse through the tests related to a specific scenario. I don't think there is a hard limit here, just as there is no hard limit for the size of production classes or the number of methods. I personally put the limits higher for test code than for production code, because test code tends to be simpler, so the threshold where it starts to become difficult to understand is higher. But in general, a 1000 line test class with 50 test methods starts to feel too big for me.
I just recently had to work with such a test class, and I ended up partitioning it, so now I have several test classes each testing one particular method / use case of a specific class*. Some of the old tests I managed to convert into parameterized tests, and all new tests are written as paramterized tests. I found that parameterized tests make it much easier to look through the big picture, and keep all test cases in mind at once. I did this using JUnit on a Java project, but I see NUnit 2.5 now offers parameterized tests too - you should check it out.
*You may rightly ask shouldn't the class under test be refactored if we need so many test cases to cover it - yes it should, eventually. It is the largest class in our legacy app, with way too much stuff in it. But first we need to have the test cases in place :-) Btw this may apply to your class too - if you need so many test cases to cover it, it might be that the class under test is just trying to do too much, and you would be better off extracting some of its functionality into a separate class, with its own unit tests.

Simplest, fastest way to break out all dependencies from a class

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..

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.

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.

How to unit test code that is highly complex behind the public interface

I'm wondering how I should be testing this sort of functionality via NUnit.
Public void HighlyComplexCalculationOnAListOfHairyObjects()
{
// calls 19 private methods totalling ~1000 lines code + comments + whitespace
}
From reading I see that NUnit isn't designed to test private methods for philosophical reasons about what unit testing should be; but trying to create a set of test data that fully executed all the functionality involved in the computation would be nearly impossible. Meanwhile the calculation is broken down into a number of smaller methods that are reasonably discrete. They are not however things that make logical sense to be done independently of each other so they're all set as private.

You've conflated two things. The Interface (which might expose very little) and this particular Implementation class, which might expose a lot more.
Define the narrowest possible Interface.
Define the Implementation class with testable (non-private) methods and attributes. It's okay if the class has "extra" stuff.
All applications should use the Interface, and -- consequently -- don't have type-safe access to the exposed features of the class.
What if "someone" bypasses the Interface and uses the Class directly? They are sociopaths -- you can safely ignore them. Don't provide them phone support because they violated the fundamental rule of using the Interface not the Implementation.

To solve your immediate problem, you may want to take a look at Pex, which is a tool from Microsoft Research that addresses this type of problem by finding all relevant boundary values so that all code paths can be executed.
That said, had you used Test-Driven Development (TDD), you would never had found yourself in that situation, since it would have been near-impossible to write unit tests that drives this kind of API.
A method like the one you describe sounds like it tries to do too many things at once. One of the key benefits of TDD is that it drives you to implement your code from small, composable objects instead of big classes with inflexible interfaces.

As mentioned, InternalsVisibleTo("AssemblyName") is a good place to start when testing legacy code.
Internal methods are still private in the sense that assemblys outside of the current assembly cannot see the methods. Check MSDN for more infomation.
Another thing would be to refactor the large method into smaller, more defined classes. Check this question I asked about a similiar problem, testing large methods.

Personally I'd make the constituent methods internal, apply InternalsVisibleTo and test the different bits.
White-box unit testing can certainly still be effective - although it's generally more brittle than black-box testing (i.e. you're more likely to have to change the tests if you change the implementation).

HighlyComplexCalculationOnAListOfHairyObjects() is a code smell, an indication that the class that contains it is potentially doing too much and should be refactored via Extract Class. The methods of this new class would be public, and therefore testable as units.
One issue to such a refactoring is that the original class held a lot of state that the new class would need. Which is another code smell, one that indicates that state should be moved into a value object.

I've seen (and probably written) many such hair objects. If it's hard to test, it's usually a good candidate for refactoring. Of course, one problem with that is that the first step to refactoring is making sure it passes all tests first.
Honestly, though, I'd look to see if there isn't some way you can break that code down into a more manageable section.

Get the book Working Effectively with Legacy Code by Michael Feathers. I'm about a third of the way through it, and it has multiple techniques for dealing with these types of problems.

Your question implies that there are many paths of execution throughout the subsystem. The first idea that pops into mind is "refactor." Even if your API remains a one-method interface, testing shouldn't be "impossible".

trying to create a set of test data
that fully executed all the
functionality involved in the
computation would be nearly impossible
If that's true, try a less ambitious goal. Start by testing specific, high-usage paths through the code, paths that you suspect may be fragile, and paths for which you've had reported bugs.
Refactoring the method into separate sub-algorithms will make your code more testable (and might be beneficial in other ways), but if your problem is a ridiculous number of interactions between those sub-algorithms, extract method (or extract to strategy class) won't really solve it: you'll have to build up a solid suite of tests one at a time.