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I'm in the process of pushing my company towards having unit tests as a major part of the development cycle. I've gotten the testing framework working with our MVC framework, and multiple members of the team are now writing unit tests. I'm at the point, though, where there's work that needs to be done to improve our hourly build, the ease of figuring out what fixtures you need to use, adding functionality to the mock object generator, etc., etc., and I want to be able to make the case for this work to management. In addition, I'd like us to allocate time to write unit tests for the most critical pieces of existing code, and I just don't see that happening without a more specific case than "everyone knows unit tests are good".
How do you quantify the positive impact of (comprehensive and reliable) unit tests on your projects? I can certainly look at the number and severity of bugs filed and correlate it with our increases in code coverage, but that's a rather weak metric.
Sonar is a company that makes a very interesting code inspection tool, they actually try to measure technical debt programaticaly, which correlates untested code and developer price per hour.
Quantification of test-quality is very difficult.
I see code-coverage only as guidance not as test-quality metric. You can literally write test of 100% code-coverage without testing anything (e.g. no asserts are used at all). Also have a look at my blog-post where I warn against metric-pitfalls.
The only sensible quantitative metric I know of and which counts for business is really reduced effort of bug-fixes in production-code. Also reduced bug-severity. Still it is very difficult to isolate that unit-tests are the only source of this success (it could also be improvement of process or communication).
Generally I would focus on the qualitative approach:
Do developers feel more comfortable changing code (because tests are a trustworthy safety net)?
When bugs occur in production analysis really shows that it was untested code (vice versa a minor conlusion that it wouldn't have occurred if there had been unit test)
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Here is an article: https://martinfowler.com/articles/mocksArentStubs.html#ClassicalAndMockistTesting
It's in relation to Classical TDD and Mockist. My understanding was that classes should be tested in isolation therefore ALL dependencies should be stubbed / mocked. However it seems there's a large group of people the Classical TDDers who use real objects according to the article. There are various articles on the internet that emphasize that unit tests should not use real classes other than the SUT of course. For example take a look at this from Microsoft's website on stubs: https://learn.microsoft.com/en-us/visualstudio/test/using-stubs-to-isolate-parts-of-your-application-from-each-other-for-unit-testing
public int GetContosoPrice()
{
var stockFeed = new StockFeed(); // NOT RECOMMENDED
return stockFeed.GetSharePrice("COOO");
}
Can someone clear up my confusion?
Can someone clear up the my confusion?
You don't seem to be confused at all - there are two different schools of thought on what a "unit test" is, and therefore how it should be used.
For instance, Kent Beck, in Test Driven Development By Example, writes
The problem with driving development with small-scale tests ( I call them "unit tests" but they don't match the accepted definition of unit tests very well)....
Emphasis added.
It may help to keep in mind that 20 years ago, the most common testing pattern was the "throw it over the wall to QA" test. Even in cases where automated tests were present, the disciplines required to make those tests effective were not common knowledge.
So it was important to communicate the idea that tests should be isolated from other tests. If developers were going to be running tests as often as the extreme programmers were insisting that they should, then those tests needed to be reliable and fast in wall clock time. Tests that don't share any mutable state (either themselves, or indirectly via the system under test) can be run effectively in parallel, reducing the wall clock time, and therefore reducing the developer interruption that they introduce.
There is a separate discipline that says, in addition to the isolation described above, we should also be striving for tests that check the system in isolation from other parts of the system.
If you want to get a real sense for the history of people with these different ideas talking past each other -- including the history of recognizing that they are talking past each other and trying to invent new labels, a good starting point is the C2 wiki
http://wiki.c2.com/?UnitTest
http://wiki.c2.com/?ShouldUnitTestsTestInteroperations
http://wiki.c2.com/?DeveloperTest
http://wiki.c2.com/?ProgrammerTest
For a modern perspective, you might start with Ham Vocke's Practical Test Pyramid
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I get the concept of unit testing and TDD on a whole.
However, I'm still a little confused on what exactly unit testing frameworks are. Whenever I read about unit testing, it's usually an explanation of what it is, followed by "oh here are the frameworks for this language, i.e JUnit".
But what does that really mean? Are framework just a sort of testing library that allows programmers to write simpler/efficient unit tests?
Also, what are the benefits of using a framework? As I understand it, unit testing is done on small chunks of code at a time, i.e a method. However, I could individually write a test for a method without using a unit testing framework. Is it maybe for standardization of testing practices?
I'm just very new to testing and unit-testing, clarification on some basic concepts would be great.
A bit of a broad question, but I think there are certain thoughts that could count as as facts for an answer:
When 5, 10, 100, ... people go forward to "work" with the same idea/concept (for example unit testing) then, most likely, certain patterns respectively best practices will evolve. People have ideas, and by trial and error they find out which of those ideas are helpful and which are not.
Then people start to communicate their ideas, and those "commonly used" patterns undergo discussions and get further refined.
And sooner or later, people start thinking "I am doing the same task over and over again; I should write a program for me to do that".
And that is how frameworks come into existence: they are tools to support certain aspects of a specific activity.
Let's give an example: using a framework like JUnit, I can completely focus on writing test cases. I don't need to worry about accumulation of failure statistics; I don't need to worry how to make sure that really all my tests are executed when I want that to happen.
I simply understand how to use the JUnit framework; and I know how to further utilize JUnit test cases in conjunction with build systems such as gradle or maven - in order to have all my unit tests executed automatically; each time I push a commit into my source code management system for example.
Of course you can re-invent the wheel here; and implement all of that yourself. But that is just a waste of time. It is like saying: "I want to move my crop to the market - let's start by building the truck myself". No. You rent or buy a pre-build truck; and you use that to do what you actually want to do (move things around).
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My team is working on the development of an application running for several years already, but no unit test has ever been coded. Now that we wish starting doing so, we realise we cannot possibly go over all the existing methods to test them because that would take years of work.
The question is : how can one decide which method absolutely need unit testing, and which doesn't?
Would you rather unit test a method that is often called or a method that is often modified?
I read that Unit Testing is rather inefficient on DAO classes. Should I restrain the tests to methods containing logic?
Most important : Will the tests put in place any useful as far as only part of the application is unit tested?
how can one decide which method absolutely need unit testing, and which doesn't?
This is a difficult question to answer without knowing about your code base and what its history and future are. But in general, write tests for the parts of the code that are hard to understand, will get modified in the near future or are known to have bugs. When testing legacy applications, the best bang for your buck is to have tests make the program both easier to maintain going forward, to fix bugs and to keep old bugs from coming back.
Would you rather unit test a method that is often called or a method that is often modified?
As stated above, it depends. Is the method that is called often trivial? Easy to understand? I would probably lean towards "often modified" just to make future development easier. But ideally both should get tested.
I read that Unit Testing is rather inefficient on DAO classes.
I don't know where you read that. Unit testing can be very efficient with DAOs if you use mock objects.
Will the tests put in place any useful as far as only part of the application is unit tested?
Any tests are useful. A program that is only 10% covered by tests is better than a program with 0% coverage. Especially if that 10% is the most important or trickiest part of the program.
If you haven't read it yet, I highly recommend Michael Feather's Working Effectively with Legacy Code where "legacy code" means code that doesn't have tests.
Some people create unit tests for getters and setters and insist on 100% code coverage.
Practical people will test those methods that need testing. What this means will depend on your intelligence and discernment of what constitutes a method that needs testing.
Some people however consider the minimum size of a unit is the class and that tests should be created to test a class (and sometimes its associated classes).
In short, forget any kind of dogmatic principle about unit testing, what matters is the quality of your code. Like agile development, its what helps you to achieve that goal that is important. So if you feel your DAO objects will not benefit from testing, then don't bother - spend that time you would have spent doing something more productive instead.
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Given that there appears to be no hard and fast rule as to what a good level of code coverage for unit tests is, what then are the benefits of using a code coverage tool such as NCover?
It is fallacious to measure software quality solely according to a code coverage percentage, as you've pointed out. But NCover allows you to examine exactly which parts of your codebase have been neglected by unit-testing. Since you should know which parts of the code are executed most frequently and which parts are most error-prone, NCover is useful for ensuring they're at least being tested.
Code Coverage, as a metric gives you two important pieces of intel:
First, it tells you what is covered by a unit test and what isn't. If you use this along with static analysis of the code, you can easily find complex code that is used often and isn't tested. Complex, frequently used code that isn't currently tested is code that you will want to add tests for.
Second, if you follow the trend of the code coverage, you can detect whether you are getting "better" at testing your code, or are introducing legacy code (i.e. untested code); You may wish to have your automated build run code analysis to let you know if the coverage percentage is decreasing (indicating that someone is checking in untested code).
Even if you have an agreed level of coverage, code coverage would only tell you if you meet that level, not if the tests are any good. But even with its limitations coverage (and the stats you can derive from it, such as CRAP (coverage over complexity, Clover can display the same data as tag cloud, tis very neat) is still useful for getting a rough idea how how well the code is tested and if where potential bugs will be hiding.
No silver bullets exists, but that does not mean you should not use of every regular bullet you can find. Bind them together (Code coverage with CI, trends and coverage over complexity and maybe some code mutation) and you end up with a powerful method to quickly informing you of potential issues.
The main advantage of running a coverage tool on your test suite is to find areas of your code that are poorly tested. I often look at my coverage numbers by assembly, namespace, and class to find code that hasn't been tested, but really should be.
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Soon I will be involved in a project that will be using the agile project management/development approach, with 5 (or so) 2 week sprints. The project will be using a DDD design pattern which I have found in the past works great with unit testing, hence I have enthusiasim to use it for this project as well. The only problem is given the following factors I am unsure as to whether unit testing can be successfully implemented with agile development:
Potential for constantly changing requirements (requirements change, tests break, tests need to be updated too).
Time factor (unit tests can make dev take a fair bit longer and if requirements change towards the end of a sprint there may be too little time to update tests and production code at the best quality).
I have a feeling that if/when requirements change (especially if towards the end of a sprint) and given the tight deadlines unit tests will become a burden. Anyone have any good advice on the matter?
I think it cuts both ways. On one hand, yes, unit tests are extra code which requires extra maintenance, and will slow you down a bit. On the other hand, if requirements start evolving, having unit tests in place will be a life saver in making sure what you are changing still works.
Unless you have unit tests with high coverage, the cost of change will grow exponentially as the projects moves forward. So basically, the more change you anticipate the MORE you will actually need your unit tests.
Secondly, good unit tests depend on very few and small feature pieces in your production code. When this is true, only a few tests will be impacted when a feature changes. Basically, each test tests just one thing and small piece of production code. The key to writing unit tests that follow this principle is to decouple your code and test in isolation.
Thirdly, you need to get a better understanding of the concept of DONE and why its definition is so important in terms of sustainable development. Basically, you can't go fast over time in a sustainable fashion if your team compromizes the concept of DONE in the short term.
Considering 10+ weeks worth of code with no test coverage makes me cringe. When will you have time to manually test all that code? And under evolving requirements, you will use a lot more time tracking down impacts the changes will have throughout your code base.
I cannot advice strongly enough to use unit testing. Even when doing DDD, let unit tests drive implementation. Coupled with good patterns like DI/IoC and SRP, you should find both your code base and tests to be more resilient to change, and thus save you a lot of time throughout those sprints.