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We use StyleCop to enforce documentation of our code.
StyleCop (out of the box) requires properties and methods to be documented. Theoretically, interfaces and their concretions can have different headers but in practice they're usually identical.
However, when an interface is implemented in the concretion, the header isn't copied over meaning that it has to be done manually. Is there a better way to automate this rather than having to copy over each one?
Obviously we could simply copy the interface code en masse but you lose a lot of the stub code so it isn't really a perfect solution.
You can use Ghostdoc, an addin for Visual Studio. After installed it, just right click to the properties, classes or methods and click "Document This".
If you have long properties or methods you can use Resharper to auto implement and copy the interface documentations.
I found that Atomineer Pro Documentation does this nicely. I believe the statement in the overview summarizes what you have asked.
Intelligent automatic duplication of existing documentation for
overrides of interface and base class methods, throughout groups of
overloaded methods, and across related parameters within a class to
maximise documentation consistency with minimal effort.
There is a free trial if you want to take it for a test run and see if it meets your needs.
Comparison
I'm learning C# and coming from a Java world, I was a little confused to see that C# doesn't have a "package private". Most comments I've seen regarding this amount to "You cannot do it; the language wasn't designed this way". I also saw some workarounds that involve internal and partial along with comments that said these workarounds go against the language's design.
Why was C# designed this way? Also, how would I do something like the following: I have a Product class and a ProductInstance class. The only way I want a ProductInstance to be created is via a factory method in the Product class. In Java, I would put ProductInstance in the same package as Product, but make its constructor package private so that only Product would have access to it. This way, anyone who wants to create a ProductInstance can only do so via the factory method in the Product class. How would I accomplish the same thing in C#?
internal is what you are after. It means the member is accessible by any class in the same assembly. There is nothing wrong with using it for this purpose (Product & ProductInstance), and is one of the things for which it was designed. C# chose not to make namespaces significant -- they are used for organization, not to determine what types can see one another, as in java with package private.
partial is nothing at all like internal or package private. It is simply a way to split the implementation of a class into multiple files, with some extensibility options thrown in for good measure.
Packages don't really exist in the same way as they do in Java. Namespaces are used to organize code and prevent naming clashes, but not for access control. Projects/assemblies can be used for access control, but you can't have nested projects/assemblies like you can with packages.
Use internal to hide one project's members from another.
Is there a concept in C# of class definition and implementation similar to what you find in C++?
I prefer to keep my class definitions simple by removing most, if no every, implementations details (it depends on several factors as you may know, but generally I move towards leaving most member implementation details outside the class definition). This has the benefit of giving me a bird's eye view of the class and its functionality.
However in C# it seems I'm forced to define my member functions at the point of declaration. Can this be avoided, or circumvent some way?
During my apprenticeship of C#, this is one aspect that is bothering me. Classes, especially complex ones, become increasingly harder to read.
This is really a case of needing to step back and see the bigger picture. Visual studio has many, many tools to help you write and manipulate your code, from outlining, #regions, class view, class diagrams, the Code Definition Window and many more.
C# isn't C++, if you try to make it so then you'll trip over yourself and no-one else will be able to read your code.
A day spent learning to use the Visual Studio tools will repay the investment many times over in terms of productivity and you'll soon wonder how you ever lived with that C++ way of doing things.
Update in response to comments
I have long since stopped regarding my code as simple text files. I regard code as an organic thing and I find that allowing myself to rely on a feature-rich IDE lets me move up and down levels of abstraction more easily and enhances my productivity no end. I suppose that could be a personal trait and perhaps it is not for everyone; I have a very 'visual' mind and I work best when I can see things in pictures.
That said, a clever IDE is not an excuse for poor style. There are best practices for writing "clean code" that don't require an smart IDE. One of the principles of clean code is to keep the definition of something near its use and I think that could be extended to cover declaration and definition. Personally, I think that separating the declaration and definition makes the code less clear. If you are finding that you get monster classes that are hard to understand, then that might be a sign that you're violating the Single Responsibility Principle.
The reason for separate definition and declaration in c/C++ is because C++ uses a single pass compiler, where forward references cannot be resolved later, unlike C# and its two-pass compiler which can happily find references regardless of the order of declaration. This difference stems from the different design philosphies of the compilers: C/C++ considers each source file to be a unit of compilation, whereas in C# the entire project is considered to be the unit of compilation. I suppose when you are used to working in the C/C++ way then separating the declaration and definition can appear to be a desirable element of style, but I personally believe that keeping declaration and use (or in this case declaration and definition) enhances, rather then reduces, readability. I used to be a C programmer myself until I started using C# in 2001. I always loved C and thought it's way of doing things was the 'bees knees'. These days when I read C/C++ code I think it looks absolutely horrendous and I can't believe we used to put up with working that way. It's all a matter of what you are used to, I suppose.
If you're using Visual Studio, you can take advantage of the Class View. You can also use the expand/collapse features of the source code editor.
In the improbable case that your tools don't help, you can always write a quick utility that will summarize the class for you.
If the class has been compiled, you can use Reflector to view the class, too.
No, there is no concept of implementation and header files in C# like you find in C/C++. The closest you can come to this is to use an interface, but the interface can only define the public members of your class. You would then end up with a 1-to-1 mapping of classes and interfaces, which really isn't the intent for how interfaces are to be used.
You could get a similar result by defining an interface for each of your classes which they then implement.
It sounds like you're referring to interfaces. In c#, you can define all of your member functions in an interface, and then implement them in another class.
In C# you could fake it with partial classes and partial members to a point, however, forward declarations and prototypes go the way of the dodo bird with your newer languages. Class View, Class Diagrams, Intellisense, et al, all help to remove the potential need for those "features".
Define an interface.
Then it's nice to be able to automatically implement the interface using a nice code assist tool.
If you find that a class is hard to read or difficult to understand, that's often a sign that the class is trying to do too much. Instead of trying to duplicate C++'s separation of declarations and definitions, consider refactoring the troublesome class into several classes so that each class has less responsibility.
Whenever it's possible or desirable, I'll go with the previous responses and define an interface. but it's not always appropriate.
alternatively, you can work around this "problem" by using some static code inspection tools. Resharper's "File Structure" window will give you exactly what you want. you can also use the built in "Class View" from visual studio. but I prefer the former.
The prototyping that I guess you are referring to does not really exist in C#. Defining interfaces as others have suggested will give you a point where you have declarations of your methods collected, but it's not the same thing as prototypes, and I am not so sure that it will help you in making your implementation classes easier to read.
C# is not C++, and should probably not be treated as C++.
Not sure what you mean by your classes continue to grow and become hard to read. Do you mean you want a header file like view of a class's members? If so, like John suggested, can't you just collapse the implementation so you don't have to see it?
If you don't want every class to implement a certain thing, then interfaces are probably the way to go (like others are saying).
But as a side thought, if your classes themselves get more and more complex as a your write the program, perhaps it's more of a design issue than a language problem? I think a class should have one responsibility and not take on more and more responsibilities as the program grows, rather the number of classes and how old classes are used should grow and get more complex as you continue to develop your software?
There are two remedies for this to make it more C++-ish:
Create an interface file that declares all method signatures and properties
Implement that interface in a class across multiple files by using the partial modifier on the class definitions
Edits:
// File: ICppLikeInterface.cs
public interface ICppLikeInterface
{
...
}
// File: CppLikeImplementation1.cs
public partial class CppLikeImplementation : ICppLikeInterface
{
...
}
// File: CppLikeImplementation2.cs
public partial class CppLikeImplementation : ICppLikeInterface
{
...
}
The C++ way of separating interface into a header file is mostly (I think) due to an early design decision when C was created to allow fast, incremental compilations during the "old days", as the compiler throws away any meta data, contrary to Smalltalk. This is not a matter with C# (nor Java) where tens of thousands of lines compiles within seconds on recent hardware (C++ still doesn't)
This question already has answers here:
Unit testing private methods in C#
(17 answers)
Closed 6 years ago.
I am currently involved in developing with C# - Here is some background:
We implement MVP with our client application and we have a cyclomatic rule which states that no method should have a cyclomatic complexity greater than 5.
This leads to a lot of small private methods which are generally responsible for one thing.
My question is about unit testing a class:
Testing the private implementation through the public methods is all fine... I don't have a problem implementing this.
But... what about the following cases:
Example 1. Handle the result of an async data retrival request (The callback method shouldn't be public purely for testing)
Example 2. An event handler which does an operation (such as update a View label's text - silly example I know...)
Example 3. You are using a third party framework which allows you to extend by overriding protected virtual methods (the path from the public methods to these virtual methods are generally treated as black box programming and will have all sorts of dependancies that the framework provides that you don't want to know about)
The examples above don't appear to me to be the result of poor design.
They also do not appear be be candidates for moving to a seperate class for testing in isolation as such methods will lose their context.
Doesn anyone have any thoughts about this?
Cheers,
Jason
EDIT:
I don't think I was clear enough in my original question - I can test private methods using accessors and mock out calls/ methods using TypeMock. That isn't the problem. The problem is testing things which don't need to be public, or can't be public.
I don't want to make code public for the sake of testing as it can introduce security loopholes (only publishing an interface to hide this is not an option because anyone can just cast the object back to its original type and get access to stuff I wouldn't want them to)
Code that gets refactored out to another class for testing is fine - but can lose context. I've always thought it bad practice to have 'helper' classes which can contain a pot of code with no specific context - (thinking SRP here). I really don't think this works for event handlers either.
I am happy to be proven wrong - I just am unsure how to test this functionality! I have always been of the mind that if it can break or be changed - test it.
Cheers, Jason
As Chris has stated, it is standard practice to only unit test public methods. This is because, as a consumer of that object, you are only concerned about what is publically available to you. And, in theory, proper unit tests with edge cases will fully exercise all private method dependencies they have.
That being said, I find there are a few times where writing unit tests directly against private methods can be extremely useful, and most succinct in explaining, through your unit tests, some of the more complex scenarios or edge cases that might be encountered.
If that is the case, you can still invoke private methods using reflection.
MyClass obj = new MyClass();
MethodInfo methodInfo = obj.GetType().GetMethod("MethodName", BindingFlags.Instance | BindingFlags.NonPublic);
object result = methodInfo.Invoke(obj, new object[] { "asdf", 1, 2 });
// assert your expected result against the one above
we have a cyclomatic rule which states
that no method should have a
cyclomatic complexity greater than 5
I like that rule.
The point is that the private methods are implementation details. They are subject to change/refactoring. You want to test the public interface.
If you have private methods with complex logic, consider refactoring them out into a separate class. That can also help keep cyclomatic complexity down. Another option is to make the method internal and use InternalsVisibleTo (mentioned in one of the links in Chris's answer).
The catches tend to come in when you have external dependencies referenced in private methods. In most cases you can use techniques such as Dependency Injection to decouple your classes. For your example with the third-party framework, that might be difficult. I'd try first to refactor the design to separate the third-party dependencies. If that's not possible, consider using Typemock Isolator. I haven't used it, but its key feature is being able to "mock" out private, static, etc. methods.
Classes are black boxes. Test them that way.
EDIT: I'll try to respond to Jason's comment on my answer and the edit to the original question. First, I think SRP pushes towards more classes, not away from them. Yes, Swiss Army helper classes are best avoided. But what about a class designed to handle async operations? Or a data retrieval class? Are these part of the responsibility of the original class, or can they be separated?
For example, say you move this logic to another class (which could be internal). That class implements an Asynchronous Design Pattern that permits the caller to choose if the method is called synchronously or asynchronously. Unit tests or integration tests are written against the synchronous method. The asynchronous calls use a standard pattern and have low complexity; we don't test those (except in acceptance tests). If the async class is internal, use InternalsVisibleTo to test it.
There is really only two cases you need to consider:
the private code is called, directly or indirectly from public code and
the private code is not called from public code.
In the first case, the private code is automatically being tested by the tests which exercise the public code that calls the private code, so there is no need to test the private code. And in the second case, the private code cannot be called at all, therefore it should be deleted, not tested.
Ergo: there is no need to explicitly test the private code.
Note that when you do TDD it is impossible for untested private code to even exist. Because when you do TDD, the only way that private code can be appear, is by an Extract {Method|Class|...} Refactoring from public code. And Refactorings are, by definition, behavior-preserving and therefore test-coverage-preserving. And the only way that public code can appear is as the result of a failing test. If public code can only appear as already tested code as the result of a failing test, and private code can only appear as the result of being extracted from public code via a behavior-preserving refactoring, it follows that untested private code can never appear.
In all of my unit testing, I've never bothered testing private functions. I typically just tested public functions. This goes along with the Black Box Testing methodology.
You are correct that you really can't test the private functions unless you expose the private class.
If your "seperate class for testing" is in the same assembly, you can choose to use internal instead of private. This exposes the internal methods to your code, but they methods will not be accessible to code not in your assembly.
EDIT: searching SO for this topic I came across this question. The most voted answer is similar to my response.
A few points from a TDD guy who has been banging around in C#:
1) If you program to interfaces then any method of a class that is not in the interface is effectively private. You might find this a better way to promote testability and a better way to use interfaces as well. Test these as public members.
2) Those small helper methods may more properly belong to some other class. Look for feature envy. What may not be reasonable as a private member of the original class (in which you found it) may be a reasonable public method of the class it envies. Test these in the new class as public members.
3) If you examine a number of small private methods, you might find that they have cohesion. They may represent a smaller class of interest separate from the original class. If so, that class can have all public methods, but be either held as a private member of the original class or perhaps created and destroyed in functions. Test these in the new class as public members.
4) You can derive a "Testable" class from the original, in which it is a trivial task to create a new public method that does nothing but call the old, private method. The testable class is part of the test framework, and not part of the production code, so it is cool for it to have special access. Test it in the test framework as if it were public.
All of these make it pretty trivial to have tests on the methods that are currently private helper methods, without messing up the way intellisense works.
There are some great answers here, and I basically agree with the repeated advice to sprout new classes. For your Example 3, however, there's a sneaky, simple technique:
Example 3. You are using a third party
framework which allows you to extend
by overriding protected virtual
methods (the path from the public
methods to these virtual methods are
generally treated as black box
programming and will have all sorts of
dependencies that the framework
provides that you don't want to know
about)
Let's say MyClass extends FrameworkClass. Have MyTestableClass extend MyClass, and then provide public methods in MyTestableClass that expose the protected methods of MyClass that you need. Not a great practice - it's kind of an enabler for bad design - but useful on occasion, and very simple.
Would accessor files work? http://msdn.microsoft.com/en-us/library/bb514191.aspx I've never directly worked with them, but I know a coworker used them to test private methods on some Windows Forms.
Several people have responded that private methods shouldn't be tested directly, or they should be moved to another class. While I think this is good, sometimes its just not worth it. While I agree with this in principle, I've found that this is one of those rules that cna be broken to save time without negative repercussions. If the function is small/simple the overhead of creating another class and test class is overkill. I will make these private methods public, but then not add them to the interface. This way consumers of the class (who should be getting the interface only through my IoC library) won't accidentally use them, but they're available for testing.
Now in the case of callbacks, this is a great example where making a private property public can make tests a lot easier to write and maintain. For instance, if class A passes a callback to class B, I'll make that callback a public property of class A. One test for class A use a stub implementation for B that records the callback passed in. The test then verify the the callback is passed in to B under appropriate conditions. A separate test for class A can then call the callback directly, verifying it has the appropriate side effects.
I think this approach works great for verifying async behaviors, I've been doing it in some javascript tests and some lua tests. The benefit is I have two small simple tests (one that verifies the callback is setup, one that verifies it behaves as expected). If you try to keep the callback private then the test verifying the callback behavior has a lot more setup to do, and that setup will overlap with behavior that should be in other tests. Bad coupling.
I know, its not pretty, but I think it works well.
I will admit that when recently writing units tests for C# I discovered that many of the tricks I knew for Java did not really apply (in my case it was testing internal classes).
For example 1, if you can fake/mock the data retrieval handler you can get access to the callback through the fake. (Most other languages I know that use callbacks also tend not to make them private).
For example 2 I would look into firing the event to test the handler.
Example 3 is an example of the Template Pattern which does exist in other languages. I have seen two ways to do this:
Test the entire class anyway (or at least relevant pieces of it). This particularly works in cases where the abstract base class comes with its own tests, or the overall class is not too complex. In Java I might do this if I were writing an extension of AbstractList, for example. This may also be the case if the template pattern was generated by refactoring.
Extend the class again with extra hooks that allow calling the protected methods directly.
Don't test private code, or you'll be sorry later when it's time to refactor. Then, you'll do like Joel and blog about how TDD is too much work because you constantly have to refactor your tests with your code.
There are techniques (mocks, stub) to do proper black box testing. Look them up.
This is a question that comes up pretty early when introducing testing. The best technique to solving this problem is to black-box test (as mentioned above) and follow the single responsibility principle. If each of your classes only have only one reason to change, they should be pretty easy to test their behavior without getting at their private methods.
SRP - wikipedia / pdf
This also leads to more robust and adaptable code as the single responsibility principle is really just saying that your class should have high cohesion.
In C# you can use the attribute in AssemblyInfo.cs:
[assembly: InternalsVisibleTo("Worker.Tests")]
Simply mark your private methods with internal, and the test project will still see the method. Simple! You get to keep encapsulation AND have testing, without all the TDD nonsense.
I'm trying to do something rather... unique, and maybe there's a far better way to do it but... I'm doing an inversion of control(ish) system that uses extension methods to enable/disable components of the class, so before I get into more detail and confuse you, lets look at some code!
using TestComponents.CommunicationProtocols.RS232;
//this brings in the
//ConnectRS232 extension method
namespace TestMeNamespace
{
public class Test //Although this class is defined here, we extend it above
{
public void Start()
{
this.ConnectRS232(1, 9600); //calls the ConnectRS232 extension method
}
}
}
So in short, the using declaration extends Test in the same file that we DEFINE test.
(inheritance would be fine as well) However there are some problems with this! first of all, the ugly requisite "this". blech. secondly it's a messy co-dependant system.
Here's what I'm attempting to achieve:
I want a way to easily extend static methods to a class (using declarations are fine)
I want to make statements simple: ConnectRS232();
I want to not have to futz with partial classes if I don't have to.
I'd be fine with using interface inheritance.
Feel free to ask me additional questions via comments but please don't post an answer unless you have an ANSWER!
Edit: In lieu of questions raised, I'm doing some JIT compilation of C#script (www.cs-script.com) in my system, and also these scripts will be mostly written by non-programmers who have been using a really "special" proprietary language for scripting for years. I want to keep things simple as hell, and a whole bunch of "this" calls look like clutter.
I'm not sure I see the point in this...
Your "extensions" will be compile time only. The extension methods only work as static methods, and since you're building this on importing of namespaces, it's more of a compile time construct than any form of IoC. (Extension methods are just a compile time thing - they don't really do anything at runtime.)
Also, given the above statement, having this.Method() doesn't seem onerous (it's good practice to use normally, which is why tools such as StyleCop enforce that you do that on EVERY method call).
Can you give us a better example of how this would be used? Right now, it just seems like a way to put code in two places instead of one, with no real benefit...