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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.
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.
So I've written a class and I have the code to test it, but where should I put that code? I could make a static method Test() for the class, but that doesn't need to be there during production and clutters up the class declaration. A bit of searching told me to put the test code in a separate project, but what exactly would the format of that project be? One static class with a method for each of the classes, so if my class was called Randomizer, the method would be called testRandomizer?
What are some best practices regarding organizing test code?
EDIT: I originally tagged the question with a variety of languages to which I thought it was relevant, but it seems like the overall answer to the question may be "use a testing framework", which is language specific. :D
Whether you are using a test framework (I highly recommend doing so) or not, the best place for the unit tests is in a separate assembly (C/C++/C#) or package (Java).
You will only have access to public and protected classes and methods, however unit testing usually only tests public APIs.
I recommend you add a separate test project/assembly/package for each existing project/assembly/package.
The format of the project depends on the test framework - for a .NET test project, use VSs built in test project template or NUnit in your version of VS doesn't support unit testing, for Java use JUnit, for C/C++ perhaps CppUnit (I haven't tried this one).
Test projects usually contain one static class init methods, one static class tear down method, one non-static init method for all tests, one non-static tear down method for all tests and one non-static method per test + any other methods you add.
The static methods let you copy dlls, set up the test environment and clear up the test enviroment, the non-static shared methods are for reducing duplicate code and the actual test methods for preparing the test-specific input, expected output and comparing them.
Where you put your test code depends on what you intend to do with the code. If it's a stand-alone class that, for example, you intend to make available to others for download and use, then the test code should be a project within the solution. The test code would, in addition to providing verification that the class was doing what you wanted it to do, provide an example for users of your class, so it should be well-documented and extremely clear.
If, on the other hand, your class is part of a library or DLL, and is intended to work only within the ecosystem of that library or DLL, then there should be a test program or framework that exercises the DLL as an entity. Code coverage tools will demonstrate that the test code is actually exercising the code. In my experience, these test programs are, like the single class program, built as a project within the solution that builds the DLL or library.
Note that in both of the above cases, the test project is not built as part of the standard build process. You have to build it specifically.
Finally, if your class is to be part of a larger project, your test code should become a part of whatever framework or process flow has been defined for your greater team. On my current project, for example, developer unit tests are maintained in a separate source control tree that has a structure parallel to that of the shipping code. Unit tests are required to pass code review by both the development and test team. During the build process (every other day right now), we build the shipping code, then the unit tests, then the QA test code set. Unit tests are run before the QA code and all must pass. This is pretty much a smoke test to make sure that we haven't broken the lowest level of functionality. Unit tests are required to generate a failure report and exit with a negative status code. Our processes are probably more formal than many, though.
In Java you should use Junit4, either by itself or (I think better) with an IDE. We have used three environments : Eclipse, NetBeans and Maven (with and without IDE). There can be some slight incompatibilities between these if not deployed systematically.
Generally all tests are in the same project but under a different directory/folder. Thus a class:
org.foo.Bar.java
would have a test
org.foo.BarTest.java
These are in the same package (org.foo) but would be organized in directories:
src/main/java/org/foo/Bar.java
and
src/test/java/org/foo/BarTest.java
These directories are universally recognised by Eclipse, NetBeans and Maven. Maven is the pickiest, whereas Eclipse does not always enforce strictness.
You should probably avoid calling other classes TestPlugh or XyzzyTest as some (old) tools will pick these up as containing tests even if they don't.
Even if you only have one test for your method (and most test authorities would expect more to exercise edge cases) you should arrange this type of structure.
EDIT Note that Maven is able to create distributions without tests even if they are in the same package. By default Maven also requires all tests to pass before the project can be deployed.
Most setups I have seen or use have a separate project that has the tests in them. This makes it a lot easier and cleaner to work with. As a separate project it's easy to deploy your code without having to worry about the tests being a part of the live system.
As testing progresses, I have seen separate projects for unit tests, integration tests and regression tests. One of the main ideas for this is to keep your unit tests running as fast as possible. Integration & regression tests tend to take longer due to the nature of their tests (connecting to databases, etc...)
I typically create a parallel package structure in a distinct source tree in the same project. That way your tests have access to public, protected and even package-private members of the class under test, which is often useful to have.
For example, I might have
myproject
src
main
com.acme.myapp.model
User
com.acme.myapp.web
RegisterController
test
com.acme.myapp.model
UserTest
com.acme.myapp.web
RegisterControllerTest
Maven does this, but the approach isn't particularly tied to Maven.
This would depend on the Testing Framework that you are using. JUnit, NUnit, some other? Each one will document some way to organize the test code. Also, if you are using continuous integration then that would also affect where and how you place your test. For example, this article discusses some options.
Create a new project in the same solution as your code.
If you're working with c# then Visual Studio will do this for you if you select Test > New Test... It has a wizard which will guide you through the process.
hmm. you want to test random number generator... may be it will be better to create strong mathematical proof of correctness of algorithm. Because otherwise, you must be sure that every sequence ever generated has a desired distribution
Create separate projects for unit-tests, integration-tests and functional-tests. Even if your "real" code has multiple projects, you can probably do with one project for each test-type, but it is important to distinguish between each type of test.
For the unit-tests, you should create a parallel namespace-hierarchy. So if you have crazy.juggler.drummer.Customer, you should unit-test it in crazy.juggler.drummer.CustomerTest. That way it is easy to see which classes are properly tested.
Functional- and integration-tests may be harder to place, but usually you can find a proper place. Tests of the database-layer probably belong somewhere like my.app.database.DatabaseIntegrationTest. Functional-tests might warrant their own namespace: my.app.functionaltests.CustomerCreationWorkflowTest.
But tip #1: be tough about separating the various kind of tests. Especially be sure to keep the collection of unit-tests separate from the integration-tests.
In the case of C# and Visual Studio 2010, you can create a test project from the templates which will be included in your project's solution. Then, you will be able to specify which tests to fire during the building of your project. All tests will live in a separate assembly.
Otherwise, you can use the NUnit Assembly, import it to your solution and start creating methods for all the object you need to test. For bigger projects, I prefer to locate these tests inside a separate assembly.
You can generate your own tests but I would strongly recommend using an existing framework.
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.
I am a TDD noob and I don't know how to solve the following problem.
I have pretty large class which generates text file in a specific format, for import into the external system. I am going to refactor this class and I want to write unit tests before.
How should these tests look like? Actually the main goal - do not break the structure of the file. But this does not mean that I should compare the contents of the file before and after?
I think you would benefit from a test that I would hesitate to call a "unit test" - although arguably it tests the current text-file-producing "unit". This would simply run the current code and do a diff between its output and a "golden master" file (which you could generate by running the test once and copying to its designated location). If there is much conditional behavior in the code, you may want to run this with several examples, each a different test case. With the existing code, by definition, all the tests should pass.
Now start to refactor. Extract a method - or better, write a test for a method that you can envision extracting, a true unit test - extract the method, and ensure that all tests, for the new small method and for the bigger system, still pass. Lather, rinse, repeat. The system tests give you a safety net that lets you go forward in the refactoring with confidence; the unit tests drive the design of the new code.
There are libraries available to make this kind of testing easier (although it's pretty easy even without them). See http://approvaltests.sourceforge.net/.
In such a case I use the following strategy:
Write a test for each method (just covering its default behavior without any error handling etc.)
Run a code coverage tool and find the blocks not covered by the tests. Write tests covering these blocks.
Do this until you get a code coverage of over 80%
Start refactoring the class (mostly generate smaller classes following the separation of concern principle).
Use Test Driven Development for writing the new classes.
Actually, that's a pretty good place to start (comparing a well known output against what is being generated by the current class).
If the single generator class can produce different results, then create one for each case.
This will ensure that you are not breaking your current generator class.
One thing that might help you is if you have the specification document for the current class. You can use that as the base of your refactoring effort.
If you haven't yet, pick up a copy of Michael Feathers' book "Working Effectively with Legacy Code". It's all about how to add tests to existing code, which is exactly what you're looking for.
But until you finish reading the book, I'd suggest starting with a regression test: create the class, have it write the file to disk, and then compare that file to a "known good" file that you've stashed in your source repository somewhere. If they don't match, fail the test.
Then start looking at the interesting decisions that your class makes. See how you can get them under test. Maybe you extract some complicated if-conditions into public functions that return bool, and you write a battery of tests to prove that, given the right inputs, that function returns the right value. Maybe generation of a particular string has some interesting logic; start testing it.
Along the way, you may find objects that want to get out. For example, you may find that the code (or the tests!) would be simpler if there was a separate class that generates a single line of output. Go with it. You've got your regression test to catch you if you screw anything up.
Work relentlessly to remove dependencies (but make sure you've got a higher-level test, like a regression test, to catch you if you make mistakes). If your class creates its own FileStream and writes to the filesystem, change it to take a TextWriter in its constructor instead, so you can write tests that pass in a StringWriter and never touch the file system. Once that's done, you can get rid of the old test that writes a file to disk (but only if you didn't break it while trying to write the new test!) If your class needs a database connection, refactor until you can write a test that passes in fake data. Etc.