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Jimmy Bogard, wrote an article: Getting value out of your unit tests, where he gives four rules:
Test names should describe the what and the why, from the user’s perspective
Tests are code too, give them some love
Don’t settle on one fixture pattern/organizational style
One Setup, Execute and Verify per Test
In your opinion these guidelines are complete? What are your guidelines for unit tests?
Please avoid specific language idioms, try to keep answers language-agnostic .
There's an entire, 850 page book called xUnit Test Patterns that deal with this topic, so it's not something that can be easily boiled down to a few hard rules (although the rules you mention are good).
A more digestible book that also covers this subject is The Art of Unit Testing.
If I may add the rules I find most important, they would be:
Use Test-Driven Development. It's the by far the most effective road towards good unit tests. Trying to retrofit unit tests unto existing code tend to be difficult at best.
Keep it simple: Ideally, a unit test should be less than 10 lines of code. If it grows to much more than 20 lines of code, you should seriously consider refactoring either the test code, or the API you are testing.
Keep it fast. Unit test suites are meant to be executed very frequently, so aim at keeping the entire suite under 10 s. That can easily mean keeping each test under 10 ms.
Writing unit-tests is simple, it is writing unit-testable code that is difficult.
The Way of Testivus
If you write code, write tests.
Don’t get stuck on unit testing dogma.
Embrace unit testing karma.
Think of code and test as one.
The test is more important than the unit.
The best time to test is when the code is fresh.
Tests not run waste away.
An imperfect test today is better than a perfect test someday.
An ugly test is better than no test.
Sometimes, the test justifies the means.
Only fools use no tools.
Good tests fail.
Break the code in test regularly to see the effectiveness of the unit tests
Take a look at the code coverage of your tests, and try to make it reasonably complete (for error cases I'd use some discretion whether to test them or not).
For many more good ideas to write unit tests, search stackoverflow.com.
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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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I'm in a project where we don't do TDD, because our bosses and the cliente are very "old styled" people. Because I can't do design through TDD but I feel fear to changes, I would like to write unit tests for my own safety. But, how those unit test would be? Do I have to write a test for each method specification for test that they do what it's supposed they do? Do I have to test for each new functionality like TDD but without design? I have a mess in my mind.
Thanks in advance.
You probably can't hurt anything by doing unit tests - regardless of how well they're done - except for one possible side-effect, and that is false confidence.
We tend not to do hardcore TDD, nevertheless the unit test coverage ranges from non-existent to moderate depending on project, and is becoming increasingly valuable as the idea settles in.
For general pointers, I'd say the following are key priorities for you right now:
Test what you know to be important
Test what you know to be fragile
Write tests to expose any new bugs, then solve the bug by making modifications that pass the test
Apply TDD where possible to any new features
Acknowledge that you can't TDD an existing project. By its nature, TDD only applies to new ground, whether that's a new product, or a new feature for a legacy product. Don't let this fact dishearten you.
Yes. TDD is yet another software development technique which happens to utilize unit testing heavily. Unit testing as a process is fine on its own without TDD behind. Not to mention, sometimes it's not even possible to do TDD yet you do write tests (think legacy systems/existing untested code testing).
But as for what you should test. Depending how deep with testing you want (can) go, you can start with end user oriented functionality, through system components testing (ie. class contracts) up to simply assuring your code does what you claim it does - that's pretty much the final, most fine-grained unit test which you'll most likely have a lot of.
In general, what to test is not an easy question, I've happened to answer several variants of that question already, to give you few tips:
test what your code does, not what it does not
if you got certain requirement, have a test covering it
test single feature at time
focus on public contract, skip private bits
Also, reading few of the top voted unit testing questions might give you some ideas on why you will benefit from testing, regardless of using TDD or not.
When you say "we don't do TDD", do you mean that others don't practise TDD or that your bosses forbid you from practising TDD? If it's the first one, then you can practise TDD as much as you want, as long as you don't try to force other people to do it. If it's the other one, then tell your bosses that they pay you to write code the best way you know how, and TDD is part of how you do that.
You can certainly write tests without practising TDD. People do it all the time. Use the old saying, "Test until fear turns to boredom". Write tests for whatever you fear might not work correctly.
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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.
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What is the one most common mistake you make while writing unit tests? Coupling? Lack of cohesion? Try to test too much functionality at once? Not testing enough functionality?
Post some example code if you have an example of that mistake
Not writing them at all.
Testing too much in one test. My unit tests often take on more of the character of integration tests by not confining themselves to the method under test.
Testing code that is present, rather than code that should be present.
I tend to test code that is present when writing unit tests. That is, I'll write a series of tests that have exceptionally high coverage and test the majority of the code that's present, but misses out on basic error conditions not covered by the code.
Writing tests that are too coupled to the code they are testing. This is especially true where I am relying on semantic coupling and things that I just assume to work for the class.
Lack of coverage -- I rarely test all the cases I should on my first pass.
Relying on some implementation detail which is not part of the tested functionality and that might change later on in the development.
Sometimes these assumptions are just too hard to factor out or too prohibitive to take into consideration and being variable.
Forgetting to put in the rounding error allowance in double comparison is probably my biggest and most annoying mistake.
Testing using just some random values instead of including testing with equivalence partitioning and boundary value analysis.
Not writing them first (ie. not going the Test Driven route)
Making two integration points tightly coupled by not using a mock object or framework.
Not getting the test fixtures neat and tidy enough - so writing the tests is harder than it should be.
Writing tests that are neither unit tests( testing only the specific method) nor acceptance tests( testing from user's perspective).
I find that tests that testing 3-4 layers of code in one test that is not grounded at concepts that biz people understand, usually lead to tests that are a burden to maintain and make people get disappointed and turned off by automated testing.
Leaving out some small detail (e.g. a hex to dec function where the unit test didn't have any letters in it...)
Well, I sometimes miss out putting out the [Test] C# attribute, and the test doesn't even get run :)
http://msdn.microsoft.com/en-us/magazine/cc163665.aspx
Unit tests with only partial code coverage.
The tests succeed, so I'm feeling good. Things are working. I move on to something else. Turns out there's an untested corner case.
Tests that depend on a quirk of the OS you happen to be on, or an unintentional side effect of a previous test.