Is Unit Testing worth the effort

Question

I am working to integrate unit testing into the development process on the team I work on and there are some sceptics  What are some good ways to convince the sceptical developers on the team of the value of Unit Testing  In my specific case we would be adding Unit Tests as we add functionality or fixed bugs  Unfortunately our code base does not lend itself to easy testing

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I wrote a very large blog post about the topic. I've found that unit testing alone isn't worth the work and usually gets cut when deadlines get closer.

Instead of talking about unit testing from the "test-after" verification point of view, we should look at the true value found when you set out to write a spec/test/idea before the implementation.

This simple idea has changed the way I write software and I wouldn't go back to the "old" way.

How test first development changed my life

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Occasionally either myself or one of my co-workers will spend a couple of hours getting to the bottom of slightly obscure bug and once the cause of the bug is found 90  of the time that code isn t unit tested   The unit test doesn t exist because the dev is cutting corners to save time  but then looses this and more debugging   Taking the small amount of time to write a unit test can save hours of future debugging

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When you said   our code base does not lend itself to easy testing  is the first sign of a code smell   Writing Unit Tests means you typically write code differently in order to make the code more testable   This is a good thing in my opinion as what I ve seen over the years in writing code that I had to write tests for  it forced me to put forth a better design

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If you are using NUnit one simple but effective demo is to run NUnit s own test suite s  in front of them  Seeing a real test suite giving a codebase a workout is worth a thousand words

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Every day in our office there is an exchange which goes something like this       Man  I just love unit tests  I ve just been able to make a bunch of changes to the way something works  and then was able to confirm I hadn t broken anything by running the test over it again       The details change daily  but the sentiment doesn t  Unit tests and test-driven development  TDD  have so many hidden and personal benefits as well as the obvious ones that you just can t really explain to somebody until they re doing it themselves    But  ignoring that  here s my attempt    Unit Tests allows you to make big changes to code quickly  You know it works now because you ve run the tests  when you make the changes you need to make  you need to get the tests working again  This saves hours   TDD helps you to realise when to stop coding  Your tests give you confidence that you ve done enough for now and can stop tweaking and move on to the next thing  The tests and the code work together to achieve better code  Your code could be bad   buggy  Your TEST could be bad   buggy  In TDD you are banking on the chances of both being bad   buggy being low  Often it s the test that needs fixing but that s still a good outcome   TDD helps with coding constipation  When faced with a large and daunting piece of work ahead writing the tests will get you moving quickly  Unit Tests help you really understand the design of the code you are working on  Instead of writing code to do something  you are starting by outlining all the conditions you are subjecting the code to and what outputs you d expect from that   Unit Tests give you instant visual feedback  we all like the feeling of all those green lights when we ve done  It s very satisfying  It s also much easier to pick up where you left off after an interruption because you can see where you got to - that next red light that needs fixing   Contrary to popular belief unit testing does not mean writing twice as much code  or coding slower  It s faster and more robust than coding without tests once you ve got the hang of it  Test code itself is usually relatively trivial and doesn t add a big overhead to what you re doing  This is one you ll only believe when you re doing it    I think it was Fowler who said   Imperfect tests  run frequently  are much better than perfect tests that are never written at all   I interpret this as giving me permission to write tests where I think they ll be most useful even if the rest of my code coverage is woefully incomplete  Good unit tests can help document and define what something is supposed to do Unit tests help with code re-use  Migrate both your code and your tests to your new project  Tweak the code till the tests run again    A lot of work I m involved with doesn t Unit Test well  web application user interactions etc    but even so we re all test infected in this shop  and happiest when we ve got our tests tied down  I can t recommend the approach highly enough

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Who are you trying to convince   Engineers or manager   If you are trying to convince your engineer co-workers I think your best bet is to appeal to their desire to make a high quality piece of software   There are numerous studies that show it finds bugs  and if they care about doing a good job  that should be enough for them   If you are trying to convince management  you will most likely have to do some kind of cost benefit reasoning saying that the cost of the defects that will be undetected is greater than the cost of writing the tests   Be sure to include intagable costs too  such as loss of customer confidence  etc

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One of the benefits of unit testing is predictability    Before unit testing I could have predicted to a great degree of accuracy how long it would take to code something  but not how how much time I would need to debug it    These days  since I can plan what tests I am going to write  I know how long coding is going to take  and at the end of coding  the system is already debugged  This brings predictability to the development process  which remove a lot of the pressure but still retains all the joy

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I recently went through the exact same experience in my workplace and found most of them knew the theoretical benefits but had to be sold on the benefits to them specifically  so here were the points I used  successfully     They save time when performing negative testing  where you handle unexpected inputs  null pointers  out of bounds values  etc   as you can do all these in a single process  They provide immediate feedback at compile time regarding the standard of the changes    They are useful for testing internal data representations that may not be exposed during normal runtime    and the big one      You might not need unit testing  but when someone else comes in and modifies the code without a full understanding it can catch a lot of the silly mistakes they might make

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If your existing code base doesn t lend itself to unit testing  and it s already in production  you might create more problems than you solve by trying to refactor all of your code so that it is unit-testable   You may be better off putting efforts towards improving your integration testing instead   There s lots of code out there that s just simpler to write without a unit test  and if a QA can validate the functionality against a requirements document  then you re done   Ship it   The classic example of this in my mind is a SqlDataReader embedded in an ASPX page linked to a GridView   The code is all in the ASPX file   The SQL is in a stored procedure   What do you unit test   If the page does what it s supposed to do  should you really redesign it into several layers so you have something to automate

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Unit testing helps a lot in projects that are larger than any one developer can hold in their head   They allow you to run the unit test suite before checkin and discover if you broke something   This cuts down a lot on instances of having to sit and twiddle your thumbs while waiting for someone else to fix a bug they checked in  or going to the hassle of reverting their change so you can get some work done   It s also immensely valuable in refactoring  so you can be sure that the refactored code passes all the tests that the original code did

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A major part of test-driven development that is often glossed over is the writing of testable code   It seems like some kind of a compromise at first  but you ll discover that testable code is also ultimately modular  maintainable and readable  If you still need help convincing people this is a nice simple presentation about the advantages of unit testing

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A major part of test-driven development that is often glossed over is the writing of testable code   It seems like some kind of a compromise at first  but you ll discover that testable code is also ultimately modular  maintainable and readable  If you still need help convincing people this is a nice simple presentation about the advantages of unit testing

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I have a point to make that I cant see above    Everyone unit tests  they don t necessarily realise it - FACT   Think about it  you write a function to maybe parse a string and remove new line characters  As a newbie developer you either run a few cases through it from the command line by implementing it in Main   or you whack together a visual front end with a button  tie up your function to a couple of text boxes and a button and see what happens   That is unit testing - basic and badly put together but you test the piece of code for a few cases    You write something more complex  It throws errors when you throw a few cases through  unit testing  and you debug into the code and trace though  You look at values as you go through and decide if they are right or wrong  This is unit testing to some degree    Unit testing here is really taking that behaviour  formalising it into a structured pattern and saving it so that you can easily re-run those tests  If you write a  proper  unit test case rather than manually testing  it takes the same amount of time  or maybe less as you get experienced  and you have it available to repeat again and again

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I wrote a very large blog post about the topic. I've found that unit testing alone isn't worth the work and usually gets cut when deadlines get closer.

Instead of talking about unit testing from the "test-after" verification point of view, we should look at the true value found when you set out to write a spec/test/idea before the implementation.

This simple idea has changed the way I write software and I wouldn't go back to the "old" way.

How test first development changed my life

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Unit testing is a lot like going to the gym   You know it is good for you  all the arguments make sense  so you start working out   There s an initial rush  which is great  but after a few days you start to wonder if it is worth the trouble   You re taking an hour out of your day to change your clothes and run on a hamster wheel and you re not sure you re really gaining anything other than sore legs and arms   Then  after maybe one or two weeks  just as the soreness is going away  a Big Deadline begins approaching   You need to spend every waking hour trying to get  useful  work done  so you cut out extraneous stuff  like going to the gym   You fall out of the habit  and by the time Big Deadline is over  you re back to square one   If you manage to make it back to the gym at all  you feel just as sore as you were the first time you went   You do some reading  to see if you re doing something wrong   You begin feel a little bit of irrational spite toward all the fit  happy people extolling the virtues of exercise   You realize that you don t have a lot in common   They don t have to drive 15 minutes out of the way to go to the gym  there is one in their building   They don t have to argue with anybody about the benefits of exercise  it is just something everybody does and accepts as important   When a Big Deadline approaches  they aren t told that exercise is unnecessary any more than your boss would ask you to stop eating   So  to answer your question  Unit Testing is usually worth the effort  but the amount of effort required isn t going to be the same for everybody   Unit Testing may require an enormous amount of effort if you are dealing with spaghetti code base in a company that doesn t actually value code quality    A lot of managers will sing Unit Testing s praises  but that doesn t mean they will stick up for it when it matters    If you are trying to introduce Unit Testing into your work and are not seeing all the sunshine and rainbows that you have been led to expect  don t blame yourself   You might need to find a new job to really make Unit Testing work for you

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Unit testing helps a lot in projects that are larger than any one developer can hold in their head   They allow you to run the unit test suite before checkin and discover if you broke something   This cuts down a lot on instances of having to sit and twiddle your thumbs while waiting for someone else to fix a bug they checked in  or going to the hassle of reverting their change so you can get some work done   It s also immensely valuable in refactoring  so you can be sure that the refactored code passes all the tests that the original code did

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One of the benefits of unit testing is predictability    Before unit testing I could have predicted to a great degree of accuracy how long it would take to code something  but not how how much time I would need to debug it    These days  since I can plan what tests I am going to write  I know how long coding is going to take  and at the end of coding  the system is already debugged  This brings predictability to the development process  which remove a lot of the pressure but still retains all the joy

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Best way to convince    find a bug  write a unit test for it  fix the bug     That particular bug is unlikely to ever appear again  and you can prove it with your test   If you do this enough  others will catch on quickly

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If your existing code base doesn t lend itself to unit testing  and it s already in production  you might create more problems than you solve by trying to refactor all of your code so that it is unit-testable   You may be better off putting efforts towards improving your integration testing instead   There s lots of code out there that s just simpler to write without a unit test  and if a QA can validate the functionality against a requirements document  then you re done   Ship it   The classic example of this in my mind is a SqlDataReader embedded in an ASPX page linked to a GridView   The code is all in the ASPX file   The SQL is in a stored procedure   What do you unit test   If the page does what it s supposed to do  should you really redesign it into several layers so you have something to automate

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thetalkingwalnut asks            What are some good ways to convince the skeptical developers on the team of the value of Unit Testing       Everyone here is going to pile on lots of reasons out of the blue why unit testing is good  However  I find that often the best way to convince someone of something is to listen to their argument and address it point by point  If you listen and help them verbalize their concerns  you can address each one and perhaps convert them to your point of view  or at the very least  leave them without a leg to stand on   Who knows  Perhaps they will convince you why unit tests aren t appropriate for your situation  Not likely  but possible   Perhaps if you post their arguments against unit tests  we can help identify the counterarguments   It s important to listen to and understand both sides of the argument  If you try to adopt unit tests too zealously without regard to people s concerns  you ll end up with a religious war  and probably really worthless unit tests   If you adopt it slowly and start by applying it where you will see the most benefit for the least cost  you might be able to demonstrate the value of unit tests and have a better chance of convincing people  I realize this isn t as easy as it sounds - it usually requires some time and careful metrics to craft a convincing argument   Unit tests are a tool  like any other  and should be applied in such a way that the benefits  catching bugs  outweigh the costs  the effort writing them   Don t use them if where they don t make sense and remember that they are only part of your arsenal of tools  e g  inspections  assertions  code analyzers  formal methods  etc   What I tell my developers is this    They can skip writing a test for a method if they have a good argument why it isn t necessary  e g  too simple to be worth it or too difficult to be worth it  and how the method will be otherwise verified  e g  inspection  assertions  formal methods  interactive integration tests   They need to consider that some verifications like inspections and formal proofs are done at a point in time and then need to be repeated every time the production code changes  whereas unit tests and assertions can be used as regression tests  written once and executed repeatedly thereafter    Sometimes I agree with them  but more often I will debate about whether a method is really too simple or too difficult to unit test    If a developer argues that a method seems too simple to fail  isn t it worth taking the 60 seconds necessary to write up a simple 5-line unit test for it  These 5 lines of code will run every night  you do nightly builds  right   for the next year or more and will be worth the effort if even just once it happens to catch a problem that may have taken 15 minutes or longer to identify and debug  Besides  writing the easy unit tests drives up the count of unit tests  which makes the developer look good  On the other hand  if a developer argues that a method seems too difficult to unit test  not worth the significant effort required   perhaps that is a good indication that the method needs to be divided up or refactored to test the easy parts  Usually  these are methods that rely on unusual resources like singletons  the current time  or external resources like a database result set  These methods usually need to be refactored into a method that gets the resource  e g  calls getTime    and a method that takes the resource as a argument  e g  takes the timestamp as a parameter   I let them skip testing the method that retrieves the resource and they instead write a unit test for the method that now takes the resource as a argument  Usually  this makes writing the unit test much simpler and therefore worthwhile to write   The developer needs to draw a  line in the sand  in how comprehensive their unit tests should be  Later in development  whenever we find a bug  they should determine if more comprehensive unit tests would have caught the problem  If so and if such bugs crop up repeatedly  they need to move the  line  toward writing more comprehensive unit tests in the future  starting with adding or expanding the unit test for the current bug   They need to find the right balance    Its important to realize the unit tests are not a silver bullet and there is such a thing as too much unit testing  At my workplace  whenever we do a lessons learned  I inevitably hear  we need to write more unit tests   Management nods in agreement because its been banged into their heads that  unit tests      good    However  we need to understand the impact of  more unit tests   A developer can only write  N lines of code a week and you need to figure out what percentage of that code should be unit test code vs production code  A lax workplace might have 10  of the code as unit tests and 90  of the code as production code  resulting in product with a lot of  albeit very buggy  features  think MS Word   On the other hand  a strict shop with 90  unit tests and 10  production code will have a rock solid product with very few features  think  vi    You may never hear reports about the latter product crashing  but that likely has as much to do with the product not selling very well as much as it has to do with the quality of the code   Worse yet  perhaps the only certainty in software development is that  change is inevitable   Assume the strict shop  90  unit tests 10  production code  creates a product that has exactly 2 features  assuming 5  of production code    1 feature   If the customer comes along and changes 1 of the features  then that change trashes 50  of the code  45  of unit tests and 5  of the production code   The lax shop  10  unit tests 90  production code  has a product with 18 features  none of which work very well  Their customer completely revamps the requirements for 4 of their features  Even though the change is 4 times as large  only half as much of the code base gets trashed   25     4 4  unit tests   20  of production code    My point is that you have to communicate that you understand that balance between too little and too much unit testing - essentially that you ve thought through both sides of the issue  If you can convince your peers and or your management of that  you gain credibility and perhaps have a better chance of winning them over

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Occasionally either myself or one of my co-workers will spend a couple of hours getting to the bottom of slightly obscure bug and once the cause of the bug is found 90  of the time that code isn t unit tested   The unit test doesn t exist because the dev is cutting corners to save time  but then looses this and more debugging   Taking the small amount of time to write a unit test can save hours of future debugging

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The whole point of unit testing is to make testing easy   It s automated    make test  and you re done   If one of the problems you face is difficult to test code  that s the best reason of all to use unit testing

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I discovered TDD a couple of years ago  and have since written all my pet projects using it   I have estimated that it takes roughly the same time to TDD a project as it takes to cowboy it together  but I have such increased confidence in the end product that I can t help a feeling of accomplishment   I also feel that it improves my design style  much more interface-oriented in case I need to mock things together  and  as the green post at the top writes  it helps with  coding constipation   when you don t know what to write next  or you have a daunting task in front of you  you can write small   Finally  I find that by far the most useful application of TDD is in the debugging  if only because you ve already developed an interrogatory framework with which you can prod the project into producing the bug in a repeatable fashion

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Make the first things you test not related to unit testing   I work mostly in Perl  so these are Perl-specific examples  but you can adapt    Does every module load and compile correctly   In Perl  this is a matter of creating a Foo t for each Foo pm in the code base that does   use ok   Foo      Is all the POD  Plain Ol  Documentation  formatted properly   Use Test  Pod to validate the validity of the formatting of all the POD in all the files    You may not think these are big things  and they re not  but I can guarantee you will catch some slop   When these tests run once an hour  and it catches someone s premature commit  you ll have people say  Hey  that s pretty cool

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When you manually test software  you normally have a small set of tests actions that you use   Eventually you ll automatically morph your input data or actions so that you navigate yourself around known issues   Unit tests should be there to remind you that things do not work correctly   I recommend writing tests before code  adding new tests data to evolve the functionality of the main code

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As a physics student i am very driven to actually prove that my code works as it is supposed to  You could either prove this logically  which increases in difficulty drastically as implementation gets more complex  or you can make an  as close as possible  empirical proof of function through good testing   If you don t provide logical proof of function  you have to test  The only alternative is to say  I think the code works

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One of the benefits of unit testing is predictability    Before unit testing I could have predicted to a great degree of accuracy how long it would take to code something  but not how how much time I would need to debug it    These days  since I can plan what tests I am going to write  I know how long coding is going to take  and at the end of coding  the system is already debugged  This brings predictability to the development process  which remove a lot of the pressure but still retains all the joy

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I m agree with the point of view opposite to the majority here  It s OK Not to Write Unit Tests Especially prototype-heavy programming  AI for example  is difficult to combine with unit testing

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When you manually test software  you normally have a small set of tests actions that you use   Eventually you ll automatically morph your input data or actions so that you navigate yourself around known issues   Unit tests should be there to remind you that things do not work correctly   I recommend writing tests before code  adding new tests data to evolve the functionality of the main code

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In short - yes   They are worth every ounce of effort    to a point   Tests are  at the end of the day  still code  and much like typical code growth  your tests will eventually need to be refactored in order to be maintainable and sustainable   There s a tonne of GOTCHAS  when it comes to unit testing  but man oh man oh man  nothing  and I mean NOTHING empowers a developer to make changes more confidently than a rich set of unit tests   I m working on a project right now     it s somewhat TDD  and we have the majority of our business rules encapuslated as tests    we have about 500 or so unit tests right now   This past iteration I had to revamp our datasource and how our desktop application interfaces with that datasource   Took me a couple days  the whole time I just kept running unit tests to see what I broke and fixed it   Make a change  Build and run your tests  fix what you broke   Wash  Rinse  Repeat as necessary   What would have traditionally taken days of QA and boat loads of stress was instead a short and enjoyable experience   Prep up front  a little bit of extra effort  and it pays 10-fold later on when you have to start dicking around with core features functionality     I bought this book - it s a Bible of xUnit Testing knowledge - tis probably one of the most referenced books on my shelf  and I consult it daily   link text

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Unit testing help you to release software with fewer bugs while reducing overall development costs  You can click the link to read more about the benefits of unit testing

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You should test as little as possible   meaning  you should write just enough unit tests to reveal intent   This often gets glossed over   Unit testing costs you   If you make changes and you have to change tests you will be less agile    Keep unit tests short and sweet     Then they have a lot of value   Too often I see lots of tests that will never break  are big and clumsy and don t offer a lot of value  they just end up slowing you down

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One great thing about unit tests is that they serve as documentation for how your code is meant to behave   Good tests are kind of like a reference implementation  and teammates can look at them to see how to integrate their code with yours

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When you said   our code base does not lend itself to easy testing  is the first sign of a code smell   Writing Unit Tests means you typically write code differently in order to make the code more testable   This is a good thing in my opinion as what I ve seen over the years in writing code that I had to write tests for  it forced me to put forth a better design

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Unit-testing is well worth the initial investment  Since starting to use unit-testing a couple of years ago  I ve found some real benefits    regression testing removes the fear of making changes to code  there s nothing like the warm glow of seeing code work or explode every time a change is made  executable code examples for other team members  and yourself in six months time    merciless refactoring - this is incredibly rewarding  try it    Code snippets can be a great help in reducing the overhead of creating tests  It isn t difficult to create snippets that enable the creation of a class outline and an associated unit-test fixture in seconds

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The whole point of unit testing is to make testing easy   It s automated    make test  and you re done   If one of the problems you face is difficult to test code  that s the best reason of all to use unit testing

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You should test as little as possible   meaning  you should write just enough unit tests to reveal intent   This often gets glossed over   Unit testing costs you   If you make changes and you have to change tests you will be less agile    Keep unit tests short and sweet     Then they have a lot of value   Too often I see lots of tests that will never break  are big and clumsy and don t offer a lot of value  they just end up slowing you down

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Unit tests are also especially useful when it comes to refactoring or re-writing a piece a code   If you have good unit tests coverage  you can refactor with confidence   Without unit tests  it is often hard to ensure the you didn t break anything

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In short - yes   They are worth every ounce of effort    to a point   Tests are  at the end of the day  still code  and much like typical code growth  your tests will eventually need to be refactored in order to be maintainable and sustainable   There s a tonne of GOTCHAS  when it comes to unit testing  but man oh man oh man  nothing  and I mean NOTHING empowers a developer to make changes more confidently than a rich set of unit tests   I m working on a project right now     it s somewhat TDD  and we have the majority of our business rules encapuslated as tests    we have about 500 or so unit tests right now   This past iteration I had to revamp our datasource and how our desktop application interfaces with that datasource   Took me a couple days  the whole time I just kept running unit tests to see what I broke and fixed it   Make a change  Build and run your tests  fix what you broke   Wash  Rinse  Repeat as necessary   What would have traditionally taken days of QA and boat loads of stress was instead a short and enjoyable experience   Prep up front  a little bit of extra effort  and it pays 10-fold later on when you have to start dicking around with core features functionality     I bought this book - it s a Bible of xUnit Testing knowledge - tis probably one of the most referenced books on my shelf  and I consult it daily   link text

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One thing no-one has mentioned yet is getting the commitment of all developers to actually run and update any existing automated test  Automated tests that you get back to and find broken because of new development looses a lot of the value and make automated testing really painful  Most of those tests will not be indicating bugs since the developer has tested the code manually  so the time spent updating them is just waste   Convincing the skeptics to not destroy the work the others are doing on unit-tests is a lot more important for getting value from the testing and might be easier   Spending hours updating tests that has broken because of new features each time you update from the repository is neither productive nor fun

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When you manually test software  you normally have a small set of tests actions that you use   Eventually you ll automatically morph your input data or actions so that you navigate yourself around known issues   Unit tests should be there to remind you that things do not work correctly   I recommend writing tests before code  adding new tests data to evolve the functionality of the main code

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Best way to convince    find a bug  write a unit test for it  fix the bug     That particular bug is unlikely to ever appear again  and you can prove it with your test   If you do this enough  others will catch on quickly

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Unit Testing is one of the most adopted methodologies for high quality code  Its contribution to a more stable  independent and documented code is well proven   Unit test code is considered and handled as an a integral part of your repository  and as such requires development and maintenance  However  developers often encounter a situation where the resources invested in unit tests where not as fruitful as one would expect  In an ideal world every method we code will have a series of tests covering it   s code and validating it   s correctness  However  usually due to time limitations we either skip some tests or write poor quality ones  In such reality  while keeping in mind the amount of resources invested in unit testing development and maintenance  one must ask himself  given the available time  which code deserve testing the most  And from the existing tests  which tests are actually worth keeping and maintaining  See here

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Every day in our office there is an exchange which goes something like this       Man  I just love unit tests  I ve just been able to make a bunch of changes to the way something works  and then was able to confirm I hadn t broken anything by running the test over it again       The details change daily  but the sentiment doesn t  Unit tests and test-driven development  TDD  have so many hidden and personal benefits as well as the obvious ones that you just can t really explain to somebody until they re doing it themselves    But  ignoring that  here s my attempt    Unit Tests allows you to make big changes to code quickly  You know it works now because you ve run the tests  when you make the changes you need to make  you need to get the tests working again  This saves hours   TDD helps you to realise when to stop coding  Your tests give you confidence that you ve done enough for now and can stop tweaking and move on to the next thing  The tests and the code work together to achieve better code  Your code could be bad   buggy  Your TEST could be bad   buggy  In TDD you are banking on the chances of both being bad   buggy being low  Often it s the test that needs fixing but that s still a good outcome   TDD helps with coding constipation  When faced with a large and daunting piece of work ahead writing the tests will get you moving quickly  Unit Tests help you really understand the design of the code you are working on  Instead of writing code to do something  you are starting by outlining all the conditions you are subjecting the code to and what outputs you d expect from that   Unit Tests give you instant visual feedback  we all like the feeling of all those green lights when we ve done  It s very satisfying  It s also much easier to pick up where you left off after an interruption because you can see where you got to - that next red light that needs fixing   Contrary to popular belief unit testing does not mean writing twice as much code  or coding slower  It s faster and more robust than coding without tests once you ve got the hang of it  Test code itself is usually relatively trivial and doesn t add a big overhead to what you re doing  This is one you ll only believe when you re doing it    I think it was Fowler who said   Imperfect tests  run frequently  are much better than perfect tests that are never written at all   I interpret this as giving me permission to write tests where I think they ll be most useful even if the rest of my code coverage is woefully incomplete  Good unit tests can help document and define what something is supposed to do Unit tests help with code re-use  Migrate both your code and your tests to your new project  Tweak the code till the tests run again    A lot of work I m involved with doesn t Unit Test well  web application user interactions etc    but even so we re all test infected in this shop  and happiest when we ve got our tests tied down  I can t recommend the approach highly enough

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Yes - Unit Testing is definitely worth the effort but you should know it s not a silver bullet   Unit Testing is work and you will have to work to keep the test updated and relevant as code changes but the value offered is worth the effort you have to put in   The ability to refactor with impunity is a huge benefit as you can always validate functionality by running your tests after any change code   The trick is to not get too hung up on exactly the unit-of-work you re testing or how you are scaffolding test requirements and when a unit-test is really a functional test  etc   People will argue about this stuff for hours on end and the reality is that any testing you do as your write code is better than not doing it   The other axiom is about quality and not quantity - I have seen code-bases with 1000 s of test that are essentially meaningless as the rest don t really test anything useful or anything domain specific like business rules  etc of the particular domain   I ve also seen codebases with 30  code coverage but the tests were relevant  meaningful and really awesome as they tested the core functionality of the code it was written for and expressed how the code should be used    One of my favorite tricks when exploring new frameworks or codebases is to write unit-tests for  it  to discover how things work   It s a great way to learn more about something new instead of reading a dry doc

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One great thing about unit tests is that they serve as documentation for how your code is meant to behave   Good tests are kind of like a reference implementation  and teammates can look at them to see how to integrate their code with yours

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As a physics student i am very driven to actually prove that my code works as it is supposed to  You could either prove this logically  which increases in difficulty drastically as implementation gets more complex  or you can make an  as close as possible  empirical proof of function through good testing   If you don t provide logical proof of function  you have to test  The only alternative is to say  I think the code works

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For years  I ve tried to convince people that they needed to write unit test for their code  Whether they wrote the tests first  as in TDD  or after they coded the functionality  I always tried to explain them all the benefits of having unit tests for code  Hardly anyone disagreed with me  You cannot disagree with something that is obvious  and any smart person will see the benefits of unit test and TDD   The problem with unit testing is that it requires a behavioral change  and it is very hard to change people s behavior  With words  you will get a lot of people to agree with you  but you won t see many changes in the way they do things   You have to convince people by doing  Your personal success will atract more people than all the arguments you may have  If they see you are not just talking about unit test or TDD  but you are doing what you preach  and you are successful  people will try to imitate you    You should also take on a lead role because no one writes unit test right the first time  so you may need to coach them on how to do it  show them the way  and the tools available to them  Help them while they write their first tests  review the tests they write on their own  and show them the tricks  idioms and patterns you ve learned through your own experiences  After a while  they will start seeing the benefits on their own  and they will change their behavior to incorporate unit tests or TDD into their toolbox   Changes won t happen over night  but with a little of patience  you may achieve your goal

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Occasionally either myself or one of my co-workers will spend a couple of hours getting to the bottom of slightly obscure bug and once the cause of the bug is found 90  of the time that code isn t unit tested   The unit test doesn t exist because the dev is cutting corners to save time  but then looses this and more debugging   Taking the small amount of time to write a unit test can save hours of future debugging

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The one thing to keep in mind about unit testing is that it s a comfort for the developer   In contrast  functional tests are for the users  whenever you add a functional test  you are testing something that the user will see  When you add a unit test  you are just making your life easier as a developer  It s a little bit of a luxury in that respect   Keep this dichotomy in mind when you have to make a choice between writing a unit or a functional test

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Who are you trying to convince   Engineers or manager   If you are trying to convince your engineer co-workers I think your best bet is to appeal to their desire to make a high quality piece of software   There are numerous studies that show it finds bugs  and if they care about doing a good job  that should be enough for them   If you are trying to convince management  you will most likely have to do some kind of cost benefit reasoning saying that the cost of the defects that will be undetected is greater than the cost of writing the tests   Be sure to include intagable costs too  such as loss of customer confidence  etc

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A major part of test-driven development that is often glossed over is the writing of testable code   It seems like some kind of a compromise at first  but you ll discover that testable code is also ultimately modular  maintainable and readable  If you still need help convincing people this is a nice simple presentation about the advantages of unit testing

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Just today  I had to change a class for which a unit test has been written previously  The test itself was well written and included test scenarios that I hadn t even thought about  Luckily all of the tests passed  and my change was quickly verified and put into the test environment with confidence

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One of the best things about unit testing is that your code will become easier to test as you do it  Preexisting code created without tests is always a challenge because since they weren t meant to be unit-tested  it s not rare to have a high level of coupling between classes  hard-to-configure objects inside your class - like an e-mail sending service reference - and so on  But don t let this bring you down  You ll see that your overall code design will become better as you start to write unit-tests  and the more you test  the more confident you ll become on making even more changes to it without fear of breaking you application or introducing bugs   There are several reasons to unit-test your code  but as time progresses  you ll find out that the time you save on testing is one of the best reasons to do it  In a system I ve just delivered  I insisted on doing automated unit-testing in spite of the claims that I d spend way more time doing the tests than I would by testing the system manually  With all my unit tests done  I run more than 400 test cases in less than 10 minutes  and every time I had to do a small change in the code  all it took me to be sure the code was still working without bugs was ten minutes  Can you imagine the time one would spend to run those 400  test cases by hand   When it comes to automated testing - be it unit testing or acceptance testing - everyone thinks it s a wasted effort to code what you can do manually  and sometimes it s true - if you plan to run your tests only once  The best part of automated testing is that you can run them several times without effort  and after the second or third run  the time and effort you ve wasted is already paid for   One last piece of advice would be to not only unit test your code  but start doing test first  see TDD and BDD for more

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With unit test suite one can make changes to code while leaving rest of the features intact  Its a great advantage  Do you use Unit test sutie and regression test suite when ever you finish coding new feature

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Unit testing works for QA guys or your managers  not for you  so it s definitely not worth it   You should focus on writing correct code  whatever it means   not test cases  Let other guys worry about those

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Best way to convince    find a bug  write a unit test for it  fix the bug     That particular bug is unlikely to ever appear again  and you can prove it with your test   If you do this enough  others will catch on quickly

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For years  I ve tried to convince people that they needed to write unit test for their code  Whether they wrote the tests first  as in TDD  or after they coded the functionality  I always tried to explain them all the benefits of having unit tests for code  Hardly anyone disagreed with me  You cannot disagree with something that is obvious  and any smart person will see the benefits of unit test and TDD   The problem with unit testing is that it requires a behavioral change  and it is very hard to change people s behavior  With words  you will get a lot of people to agree with you  but you won t see many changes in the way they do things   You have to convince people by doing  Your personal success will atract more people than all the arguments you may have  If they see you are not just talking about unit test or TDD  but you are doing what you preach  and you are successful  people will try to imitate you    You should also take on a lead role because no one writes unit test right the first time  so you may need to coach them on how to do it  show them the way  and the tools available to them  Help them while they write their first tests  review the tests they write on their own  and show them the tricks  idioms and patterns you ve learned through your own experiences  After a while  they will start seeing the benefits on their own  and they will change their behavior to incorporate unit tests or TDD into their toolbox   Changes won t happen over night  but with a little of patience  you may achieve your goal

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Unit testing is a lot like going to the gym   You know it is good for you  all the arguments make sense  so you start working out   There s an initial rush  which is great  but after a few days you start to wonder if it is worth the trouble   You re taking an hour out of your day to change your clothes and run on a hamster wheel and you re not sure you re really gaining anything other than sore legs and arms   Then  after maybe one or two weeks  just as the soreness is going away  a Big Deadline begins approaching   You need to spend every waking hour trying to get  useful  work done  so you cut out extraneous stuff  like going to the gym   You fall out of the habit  and by the time Big Deadline is over  you re back to square one   If you manage to make it back to the gym at all  you feel just as sore as you were the first time you went   You do some reading  to see if you re doing something wrong   You begin feel a little bit of irrational spite toward all the fit  happy people extolling the virtues of exercise   You realize that you don t have a lot in common   They don t have to drive 15 minutes out of the way to go to the gym  there is one in their building   They don t have to argue with anybody about the benefits of exercise  it is just something everybody does and accepts as important   When a Big Deadline approaches  they aren t told that exercise is unnecessary any more than your boss would ask you to stop eating   So  to answer your question  Unit Testing is usually worth the effort  but the amount of effort required isn t going to be the same for everybody   Unit Testing may require an enormous amount of effort if you are dealing with spaghetti code base in a company that doesn t actually value code quality    A lot of managers will sing Unit Testing s praises  but that doesn t mean they will stick up for it when it matters    If you are trying to introduce Unit Testing into your work and are not seeing all the sunshine and rainbows that you have been led to expect  don t blame yourself   You might need to find a new job to really make Unit Testing work for you

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One of the best things about unit testing is that your code will become easier to test as you do it  Preexisting code created without tests is always a challenge because since they weren t meant to be unit-tested  it s not rare to have a high level of coupling between classes  hard-to-configure objects inside your class - like an e-mail sending service reference - and so on  But don t let this bring you down  You ll see that your overall code design will become better as you start to write unit-tests  and the more you test  the more confident you ll become on making even more changes to it without fear of breaking you application or introducing bugs   There are several reasons to unit-test your code  but as time progresses  you ll find out that the time you save on testing is one of the best reasons to do it  In a system I ve just delivered  I insisted on doing automated unit-testing in spite of the claims that I d spend way more time doing the tests than I would by testing the system manually  With all my unit tests done  I run more than 400 test cases in less than 10 minutes  and every time I had to do a small change in the code  all it took me to be sure the code was still working without bugs was ten minutes  Can you imagine the time one would spend to run those 400  test cases by hand   When it comes to automated testing - be it unit testing or acceptance testing - everyone thinks it s a wasted effort to code what you can do manually  and sometimes it s true - if you plan to run your tests only once  The best part of automated testing is that you can run them several times without effort  and after the second or third run  the time and effort you ve wasted is already paid for   One last piece of advice would be to not only unit test your code  but start doing test first  see TDD and BDD for more

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I have toyed with unit testing a number of times  and I am still to be convinced that it is worth the effort given my situation    I develop websites  where much of the logic involves creating  retrieving or updating data in the database  When I have tried to  mock  the database for unit testing purposes  it has got very messy and seemed a bit pointless   When I have written unit tests around business logic  it has never really helped me in the long run  Because I largely work on projects alone  I tend to know intuitively which areas of code may be affected by something I am working on  and I test these areas manually  I want to deliver a solution to my client as quickly as possible  and unit testing often seems a waste of time  I list manual tests and walk through them myself  ticking them off as I go   I can see that it may be beneficial when a team of developers are working on a project and updating each other s code  but even then I think that if the developers are of a high quality  good communication and well-written code should often be enough

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I m working as a maintenance-engineer of a poorly documented   awful and big code base  I wish the people who wrote the code had written the unit tests for it  Each time I make a change and update the production code I m scared that I might introduce a bug for not having considered some condition  If they wrote the test making changes to the code base would be  easier and faster  at the same time the code base would be in a better state     I think unit tests prove a lot useful when writing api or frameworks that have to last for many years and to be used modified evolved by people other than the original coders

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thetalkingwalnut asks            What are some good ways to convince the skeptical developers on the team of the value of Unit Testing       Everyone here is going to pile on lots of reasons out of the blue why unit testing is good  However  I find that often the best way to convince someone of something is to listen to their argument and address it point by point  If you listen and help them verbalize their concerns  you can address each one and perhaps convert them to your point of view  or at the very least  leave them without a leg to stand on   Who knows  Perhaps they will convince you why unit tests aren t appropriate for your situation  Not likely  but possible   Perhaps if you post their arguments against unit tests  we can help identify the counterarguments   It s important to listen to and understand both sides of the argument  If you try to adopt unit tests too zealously without regard to people s concerns  you ll end up with a religious war  and probably really worthless unit tests   If you adopt it slowly and start by applying it where you will see the most benefit for the least cost  you might be able to demonstrate the value of unit tests and have a better chance of convincing people  I realize this isn t as easy as it sounds - it usually requires some time and careful metrics to craft a convincing argument   Unit tests are a tool  like any other  and should be applied in such a way that the benefits  catching bugs  outweigh the costs  the effort writing them   Don t use them if where they don t make sense and remember that they are only part of your arsenal of tools  e g  inspections  assertions  code analyzers  formal methods  etc   What I tell my developers is this    They can skip writing a test for a method if they have a good argument why it isn t necessary  e g  too simple to be worth it or too difficult to be worth it  and how the method will be otherwise verified  e g  inspection  assertions  formal methods  interactive integration tests   They need to consider that some verifications like inspections and formal proofs are done at a point in time and then need to be repeated every time the production code changes  whereas unit tests and assertions can be used as regression tests  written once and executed repeatedly thereafter    Sometimes I agree with them  but more often I will debate about whether a method is really too simple or too difficult to unit test    If a developer argues that a method seems too simple to fail  isn t it worth taking the 60 seconds necessary to write up a simple 5-line unit test for it  These 5 lines of code will run every night  you do nightly builds  right   for the next year or more and will be worth the effort if even just once it happens to catch a problem that may have taken 15 minutes or longer to identify and debug  Besides  writing the easy unit tests drives up the count of unit tests  which makes the developer look good  On the other hand  if a developer argues that a method seems too difficult to unit test  not worth the significant effort required   perhaps that is a good indication that the method needs to be divided up or refactored to test the easy parts  Usually  these are methods that rely on unusual resources like singletons  the current time  or external resources like a database result set  These methods usually need to be refactored into a method that gets the resource  e g  calls getTime    and a method that takes the resource as a argument  e g  takes the timestamp as a parameter   I let them skip testing the method that retrieves the resource and they instead write a unit test for the method that now takes the resource as a argument  Usually  this makes writing the unit test much simpler and therefore worthwhile to write   The developer needs to draw a  line in the sand  in how comprehensive their unit tests should be  Later in development  whenever we find a bug  they should determine if more comprehensive unit tests would have caught the problem  If so and if such bugs crop up repeatedly  they need to move the  line  toward writing more comprehensive unit tests in the future  starting with adding or expanding the unit test for the current bug   They need to find the right balance    Its important to realize the unit tests are not a silver bullet and there is such a thing as too much unit testing  At my workplace  whenever we do a lessons learned  I inevitably hear  we need to write more unit tests   Management nods in agreement because its been banged into their heads that  unit tests      good    However  we need to understand the impact of  more unit tests   A developer can only write  N lines of code a week and you need to figure out what percentage of that code should be unit test code vs production code  A lax workplace might have 10  of the code as unit tests and 90  of the code as production code  resulting in product with a lot of  albeit very buggy  features  think MS Word   On the other hand  a strict shop with 90  unit tests and 10  production code will have a rock solid product with very few features  think  vi    You may never hear reports about the latter product crashing  but that likely has as much to do with the product not selling very well as much as it has to do with the quality of the code   Worse yet  perhaps the only certainty in software development is that  change is inevitable   Assume the strict shop  90  unit tests 10  production code  creates a product that has exactly 2 features  assuming 5  of production code    1 feature   If the customer comes along and changes 1 of the features  then that change trashes 50  of the code  45  of unit tests and 5  of the production code   The lax shop  10  unit tests 90  production code  has a product with 18 features  none of which work very well  Their customer completely revamps the requirements for 4 of their features  Even though the change is 4 times as large  only half as much of the code base gets trashed   25     4 4  unit tests   20  of production code    My point is that you have to communicate that you understand that balance between too little and too much unit testing - essentially that you ve thought through both sides of the issue  If you can convince your peers and or your management of that  you gain credibility and perhaps have a better chance of winning them over

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I recently went through the exact same experience in my workplace and found most of them knew the theoretical benefits but had to be sold on the benefits to them specifically  so here were the points I used  successfully     They save time when performing negative testing  where you handle unexpected inputs  null pointers  out of bounds values  etc   as you can do all these in a single process  They provide immediate feedback at compile time regarding the standard of the changes    They are useful for testing internal data representations that may not be exposed during normal runtime    and the big one      You might not need unit testing  but when someone else comes in and modifies the code without a full understanding it can catch a lot of the silly mistakes they might make

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From my experience  unit tests and integration tests are a  MUST HAVE  in complex software environments   In order to convince the developers in your team to write unit tests you may want to consider integrating unit test regression analysis in your development environment  for example  in your daily build process    Once developers know that if a unit test fails they don t have to spend so much time on debugging it to find the problem  they would be more encouraged to write them   Here s a tool which provides such functionality   unit test regression analysis tool

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The one thing to keep in mind about unit testing is that it s a comfort for the developer   In contrast  functional tests are for the users  whenever you add a functional test  you are testing something that the user will see  When you add a unit test  you are just making your life easier as a developer  It s a little bit of a luxury in that respect   Keep this dichotomy in mind when you have to make a choice between writing a unit or a functional test

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Unit testing is a lot like going to the gym   You know it is good for you  all the arguments make sense  so you start working out   There s an initial rush  which is great  but after a few days you start to wonder if it is worth the trouble   You re taking an hour out of your day to change your clothes and run on a hamster wheel and you re not sure you re really gaining anything other than sore legs and arms   Then  after maybe one or two weeks  just as the soreness is going away  a Big Deadline begins approaching   You need to spend every waking hour trying to get  useful  work done  so you cut out extraneous stuff  like going to the gym   You fall out of the habit  and by the time Big Deadline is over  you re back to square one   If you manage to make it back to the gym at all  you feel just as sore as you were the first time you went   You do some reading  to see if you re doing something wrong   You begin feel a little bit of irrational spite toward all the fit  happy people extolling the virtues of exercise   You realize that you don t have a lot in common   They don t have to drive 15 minutes out of the way to go to the gym  there is one in their building   They don t have to argue with anybody about the benefits of exercise  it is just something everybody does and accepts as important   When a Big Deadline approaches  they aren t told that exercise is unnecessary any more than your boss would ask you to stop eating   So  to answer your question  Unit Testing is usually worth the effort  but the amount of effort required isn t going to be the same for everybody   Unit Testing may require an enormous amount of effort if you are dealing with spaghetti code base in a company that doesn t actually value code quality    A lot of managers will sing Unit Testing s praises  but that doesn t mean they will stick up for it when it matters    If you are trying to introduce Unit Testing into your work and are not seeing all the sunshine and rainbows that you have been led to expect  don t blame yourself   You might need to find a new job to really make Unit Testing work for you

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Unit tests are also especially useful when it comes to refactoring or re-writing a piece a code   If you have good unit tests coverage  you can refactor with confidence   Without unit tests  it is often hard to ensure the you didn t break anything

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When you manually test software  you normally have a small set of tests actions that you use   Eventually you ll automatically morph your input data or actions so that you navigate yourself around known issues   Unit tests should be there to remind you that things do not work correctly   I recommend writing tests before code  adding new tests data to evolve the functionality of the main code

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One of the best things about unit testing is that your code will become easier to test as you do it  Preexisting code created without tests is always a challenge because since they weren t meant to be unit-tested  it s not rare to have a high level of coupling between classes  hard-to-configure objects inside your class - like an e-mail sending service reference - and so on  But don t let this bring you down  You ll see that your overall code design will become better as you start to write unit-tests  and the more you test  the more confident you ll become on making even more changes to it without fear of breaking you application or introducing bugs   There are several reasons to unit-test your code  but as time progresses  you ll find out that the time you save on testing is one of the best reasons to do it  In a system I ve just delivered  I insisted on doing automated unit-testing in spite of the claims that I d spend way more time doing the tests than I would by testing the system manually  With all my unit tests done  I run more than 400 test cases in less than 10 minutes  and every time I had to do a small change in the code  all it took me to be sure the code was still working without bugs was ten minutes  Can you imagine the time one would spend to run those 400  test cases by hand   When it comes to automated testing - be it unit testing or acceptance testing - everyone thinks it s a wasted effort to code what you can do manually  and sometimes it s true - if you plan to run your tests only once  The best part of automated testing is that you can run them several times without effort  and after the second or third run  the time and effort you ve wasted is already paid for   One last piece of advice would be to not only unit test your code  but start doing test first  see TDD and BDD for more

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One of the benefits of unit testing is predictability    Before unit testing I could have predicted to a great degree of accuracy how long it would take to code something  but not how how much time I would need to debug it    These days  since I can plan what tests I am going to write  I know how long coding is going to take  and at the end of coding  the system is already debugged  This brings predictability to the development process  which remove a lot of the pressure but still retains all the joy

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Who are you trying to convince   Engineers or manager   If you are trying to convince your engineer co-workers I think your best bet is to appeal to their desire to make a high quality piece of software   There are numerous studies that show it finds bugs  and if they care about doing a good job  that should be enough for them   If you are trying to convince management  you will most likely have to do some kind of cost benefit reasoning saying that the cost of the defects that will be undetected is greater than the cost of writing the tests   Be sure to include intagable costs too  such as loss of customer confidence  etc

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As a physics student i am very driven to actually prove that my code works as it is supposed to  You could either prove this logically  which increases in difficulty drastically as implementation gets more complex  or you can make an  as close as possible  empirical proof of function through good testing   If you don t provide logical proof of function  you have to test  The only alternative is to say  I think the code works

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If your existing code base doesn t lend itself to unit testing  and it s already in production  you might create more problems than you solve by trying to refactor all of your code so that it is unit-testable   You may be better off putting efforts towards improving your integration testing instead   There s lots of code out there that s just simpler to write without a unit test  and if a QA can validate the functionality against a requirements document  then you re done   Ship it   The classic example of this in my mind is a SqlDataReader embedded in an ASPX page linked to a GridView   The code is all in the ASPX file   The SQL is in a stored procedure   What do you unit test   If the page does what it s supposed to do  should you really redesign it into several layers so you have something to automate

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I recently went through the exact same experience in my workplace and found most of them knew the theoretical benefits but had to be sold on the benefits to them specifically  so here were the points I used  successfully     They save time when performing negative testing  where you handle unexpected inputs  null pointers  out of bounds values  etc   as you can do all these in a single process  They provide immediate feedback at compile time regarding the standard of the changes    They are useful for testing internal data representations that may not be exposed during normal runtime    and the big one      You might not need unit testing  but when someone else comes in and modifies the code without a full understanding it can catch a lot of the silly mistakes they might make

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I do not know  A lot of places do not do unit test  but the quality of the code is good  Microsoft does unit test  but Bill Gates gave a blue screen at his presentation

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When you said   our code base does not lend itself to easy testing  is the first sign of a code smell   Writing Unit Tests means you typically write code differently in order to make the code more testable   This is a good thing in my opinion as what I ve seen over the years in writing code that I had to write tests for  it forced me to put forth a better design

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Every day in our office there is an exchange which goes something like this       Man  I just love unit tests  I ve just been able to make a bunch of changes to the way something works  and then was able to confirm I hadn t broken anything by running the test over it again       The details change daily  but the sentiment doesn t  Unit tests and test-driven development  TDD  have so many hidden and personal benefits as well as the obvious ones that you just can t really explain to somebody until they re doing it themselves    But  ignoring that  here s my attempt    Unit Tests allows you to make big changes to code quickly  You know it works now because you ve run the tests  when you make the changes you need to make  you need to get the tests working again  This saves hours   TDD helps you to realise when to stop coding  Your tests give you confidence that you ve done enough for now and can stop tweaking and move on to the next thing  The tests and the code work together to achieve better code  Your code could be bad   buggy  Your TEST could be bad   buggy  In TDD you are banking on the chances of both being bad   buggy being low  Often it s the test that needs fixing but that s still a good outcome   TDD helps with coding constipation  When faced with a large and daunting piece of work ahead writing the tests will get you moving quickly  Unit Tests help you really understand the design of the code you are working on  Instead of writing code to do something  you are starting by outlining all the conditions you are subjecting the code to and what outputs you d expect from that   Unit Tests give you instant visual feedback  we all like the feeling of all those green lights when we ve done  It s very satisfying  It s also much easier to pick up where you left off after an interruption because you can see where you got to - that next red light that needs fixing   Contrary to popular belief unit testing does not mean writing twice as much code  or coding slower  It s faster and more robust than coding without tests once you ve got the hang of it  Test code itself is usually relatively trivial and doesn t add a big overhead to what you re doing  This is one you ll only believe when you re doing it    I think it was Fowler who said   Imperfect tests  run frequently  are much better than perfect tests that are never written at all   I interpret this as giving me permission to write tests where I think they ll be most useful even if the rest of my code coverage is woefully incomplete  Good unit tests can help document and define what something is supposed to do Unit tests help with code re-use  Migrate both your code and your tests to your new project  Tweak the code till the tests run again    A lot of work I m involved with doesn t Unit Test well  web application user interactions etc    but even so we re all test infected in this shop  and happiest when we ve got our tests tied down  I can t recommend the approach highly enough

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As a physics student i am very driven to actually prove that my code works as it is supposed to  You could either prove this logically  which increases in difficulty drastically as implementation gets more complex  or you can make an  as close as possible  empirical proof of function through good testing   If you don t provide logical proof of function  you have to test  The only alternative is to say  I think the code works

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Yes - Unit Testing is definitely worth the effort but you should know it s not a silver bullet   Unit Testing is work and you will have to work to keep the test updated and relevant as code changes but the value offered is worth the effort you have to put in   The ability to refactor with impunity is a huge benefit as you can always validate functionality by running your tests after any change code   The trick is to not get too hung up on exactly the unit-of-work you re testing or how you are scaffolding test requirements and when a unit-test is really a functional test  etc   People will argue about this stuff for hours on end and the reality is that any testing you do as your write code is better than not doing it   The other axiom is about quality and not quantity - I have seen code-bases with 1000 s of test that are essentially meaningless as the rest don t really test anything useful or anything domain specific like business rules  etc of the particular domain   I ve also seen codebases with 30  code coverage but the tests were relevant  meaningful and really awesome as they tested the core functionality of the code it was written for and expressed how the code should be used    One of my favorite tricks when exploring new frameworks or codebases is to write unit-tests for  it  to discover how things work   It s a great way to learn more about something new instead of reading a dry doc

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With unit test suite one can make changes to code while leaving rest of the features intact  Its a great advantage  Do you use Unit test sutie and regression test suite when ever you finish coding new feature

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In short - yes   They are worth every ounce of effort    to a point   Tests are  at the end of the day  still code  and much like typical code growth  your tests will eventually need to be refactored in order to be maintainable and sustainable   There s a tonne of GOTCHAS  when it comes to unit testing  but man oh man oh man  nothing  and I mean NOTHING empowers a developer to make changes more confidently than a rich set of unit tests   I m working on a project right now     it s somewhat TDD  and we have the majority of our business rules encapuslated as tests    we have about 500 or so unit tests right now   This past iteration I had to revamp our datasource and how our desktop application interfaces with that datasource   Took me a couple days  the whole time I just kept running unit tests to see what I broke and fixed it   Make a change  Build and run your tests  fix what you broke   Wash  Rinse  Repeat as necessary   What would have traditionally taken days of QA and boat loads of stress was instead a short and enjoyable experience   Prep up front  a little bit of extra effort  and it pays 10-fold later on when you have to start dicking around with core features functionality     I bought this book - it s a Bible of xUnit Testing knowledge - tis probably one of the most referenced books on my shelf  and I consult it daily   link text

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I didn t see this in any of the other answers  but one thing I noticed is that I could debug so much faster   You don t need to drill down through your app with just the right sequence of steps to get to the code your fixing  only to find you ve made a boolean error and need to do it all again   With a unit test  you can just step directly into the code you re debugging

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Unit-testing is well worth the initial investment  Since starting to use unit-testing a couple of years ago  I ve found some real benefits    regression testing removes the fear of making changes to code  there s nothing like the warm glow of seeing code work or explode every time a change is made  executable code examples for other team members  and yourself in six months time    merciless refactoring - this is incredibly rewarding  try it    Code snippets can be a great help in reducing the overhead of creating tests  It isn t difficult to create snippets that enable the creation of a class outline and an associated unit-test fixture in seconds

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For years  I ve tried to convince people that they needed to write unit test for their code  Whether they wrote the tests first  as in TDD  or after they coded the functionality  I always tried to explain them all the benefits of having unit tests for code  Hardly anyone disagreed with me  You cannot disagree with something that is obvious  and any smart person will see the benefits of unit test and TDD   The problem with unit testing is that it requires a behavioral change  and it is very hard to change people s behavior  With words  you will get a lot of people to agree with you  but you won t see many changes in the way they do things   You have to convince people by doing  Your personal success will atract more people than all the arguments you may have  If they see you are not just talking about unit test or TDD  but you are doing what you preach  and you are successful  people will try to imitate you    You should also take on a lead role because no one writes unit test right the first time  so you may need to coach them on how to do it  show them the way  and the tools available to them  Help them while they write their first tests  review the tests they write on their own  and show them the tricks  idioms and patterns you ve learned through your own experiences  After a while  they will start seeing the benefits on their own  and they will change their behavior to incorporate unit tests or TDD into their toolbox   Changes won t happen over night  but with a little of patience  you may achieve your goal

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Unit testing helps a lot in projects that are larger than any one developer can hold in their head   They allow you to run the unit test suite before checkin and discover if you broke something   This cuts down a lot on instances of having to sit and twiddle your thumbs while waiting for someone else to fix a bug they checked in  or going to the hassle of reverting their change so you can get some work done   It s also immensely valuable in refactoring  so you can be sure that the refactored code passes all the tests that the original code did

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George Stocker  Unfortunately our code base does not lend itself to easy testing    Everyone agrees that there are benefits to unit testing but it sounds like for this code base the costs are high  If the costs are greater than the benefits then why should they be enthusiastic about it  Listen to your coworkers  maybe for them the perceived pain of unit tests is greater than the perceived value of unit tests   Specifically  try to gain value as soon as possible  and not some feel-goodery  xUnit is green  value  but clean code that users and maintainers value  Maybe you have to mandate unit tests for one iteration and then discuss if it is worth the effort or not

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With unit test suite one can make changes to code while leaving rest of the features intact  Its a great advantage  Do you use Unit test sutie and regression test suite when ever you finish coding new feature

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Yes - Unit Testing is definitely worth the effort but you should know it s not a silver bullet   Unit Testing is work and you will have to work to keep the test updated and relevant as code changes but the value offered is worth the effort you have to put in   The ability to refactor with impunity is a huge benefit as you can always validate functionality by running your tests after any change code   The trick is to not get too hung up on exactly the unit-of-work you re testing or how you are scaffolding test requirements and when a unit-test is really a functional test  etc   People will argue about this stuff for hours on end and the reality is that any testing you do as your write code is better than not doing it   The other axiom is about quality and not quantity - I have seen code-bases with 1000 s of test that are essentially meaningless as the rest don t really test anything useful or anything domain specific like business rules  etc of the particular domain   I ve also seen codebases with 30  code coverage but the tests were relevant  meaningful and really awesome as they tested the core functionality of the code it was written for and expressed how the code should be used    One of my favorite tricks when exploring new frameworks or codebases is to write unit-tests for  it  to discover how things work   It s a great way to learn more about something new instead of reading a dry doc

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You should test as little as possible   meaning  you should write just enough unit tests to reveal intent   This often gets glossed over   Unit testing costs you   If you make changes and you have to change tests you will be less agile    Keep unit tests short and sweet     Then they have a lot of value   Too often I see lots of tests that will never break  are big and clumsy and don t offer a lot of value  they just end up slowing you down

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Occasionally either myself or one of my co-workers will spend a couple of hours getting to the bottom of slightly obscure bug and once the cause of the bug is found 90  of the time that code isn t unit tested   The unit test doesn t exist because the dev is cutting corners to save time  but then looses this and more debugging   Taking the small amount of time to write a unit test can save hours of future debugging

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Unit testing works for QA guys or your managers  not for you  so it s definitely not worth it   You should focus on writing correct code  whatever it means   not test cases  Let other guys worry about those

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If you are using NUnit one simple but effective demo is to run NUnit s own test suite s  in front of them  Seeing a real test suite giving a codebase a workout is worth a thousand words

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Every day in our office there is an exchange which goes something like this       Man  I just love unit tests  I ve just been able to make a bunch of changes to the way something works  and then was able to confirm I hadn t broken anything by running the test over it again       The details change daily  but the sentiment doesn t  Unit tests and test-driven development  TDD  have so many hidden and personal benefits as well as the obvious ones that you just can t really explain to somebody until they re doing it themselves    But  ignoring that  here s my attempt    Unit Tests allows you to make big changes to code quickly  You know it works now because you ve run the tests  when you make the changes you need to make  you need to get the tests working again  This saves hours   TDD helps you to realise when to stop coding  Your tests give you confidence that you ve done enough for now and can stop tweaking and move on to the next thing  The tests and the code work together to achieve better code  Your code could be bad   buggy  Your TEST could be bad   buggy  In TDD you are banking on the chances of both being bad   buggy being low  Often it s the test that needs fixing but that s still a good outcome   TDD helps with coding constipation  When faced with a large and daunting piece of work ahead writing the tests will get you moving quickly  Unit Tests help you really understand the design of the code you are working on  Instead of writing code to do something  you are starting by outlining all the conditions you are subjecting the code to and what outputs you d expect from that   Unit Tests give you instant visual feedback  we all like the feeling of all those green lights when we ve done  It s very satisfying  It s also much easier to pick up where you left off after an interruption because you can see where you got to - that next red light that needs fixing   Contrary to popular belief unit testing does not mean writing twice as much code  or coding slower  It s faster and more robust than coding without tests once you ve got the hang of it  Test code itself is usually relatively trivial and doesn t add a big overhead to what you re doing  This is one you ll only believe when you re doing it    I think it was Fowler who said   Imperfect tests  run frequently  are much better than perfect tests that are never written at all   I interpret this as giving me permission to write tests where I think they ll be most useful even if the rest of my code coverage is woefully incomplete  Good unit tests can help document and define what something is supposed to do Unit tests help with code re-use  Migrate both your code and your tests to your new project  Tweak the code till the tests run again    A lot of work I m involved with doesn t Unit Test well  web application user interactions etc    but even so we re all test infected in this shop  and happiest when we ve got our tests tied down  I can t recommend the approach highly enough

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One thing no-one has mentioned yet is getting the commitment of all developers to actually run and update any existing automated test  Automated tests that you get back to and find broken because of new development looses a lot of the value and make automated testing really painful  Most of those tests will not be indicating bugs since the developer has tested the code manually  so the time spent updating them is just waste   Convincing the skeptics to not destroy the work the others are doing on unit-tests is a lot more important for getting value from the testing and might be easier   Spending hours updating tests that has broken because of new features each time you update from the repository is neither productive nor fun

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Yes - Unit Testing is definitely worth the effort but you should know it s not a silver bullet   Unit Testing is work and you will have to work to keep the test updated and relevant as code changes but the value offered is worth the effort you have to put in   The ability to refactor with impunity is a huge benefit as you can always validate functionality by running your tests after any change code   The trick is to not get too hung up on exactly the unit-of-work you re testing or how you are scaffolding test requirements and when a unit-test is really a functional test  etc   People will argue about this stuff for hours on end and the reality is that any testing you do as your write code is better than not doing it   The other axiom is about quality and not quantity - I have seen code-bases with 1000 s of test that are essentially meaningless as the rest don t really test anything useful or anything domain specific like business rules  etc of the particular domain   I ve also seen codebases with 30  code coverage but the tests were relevant  meaningful and really awesome as they tested the core functionality of the code it was written for and expressed how the code should be used    One of my favorite tricks when exploring new frameworks or codebases is to write unit-tests for  it  to discover how things work   It s a great way to learn more about something new instead of reading a dry doc

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When you said   our code base does not lend itself to easy testing  is the first sign of a code smell   Writing Unit Tests means you typically write code differently in order to make the code more testable   This is a good thing in my opinion as what I ve seen over the years in writing code that I had to write tests for  it forced me to put forth a better design

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One great thing about unit tests is that they serve as documentation for how your code is meant to behave   Good tests are kind of like a reference implementation  and teammates can look at them to see how to integrate their code with yours

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Unit testing helps a lot in projects that are larger than any one developer can hold in their head   They allow you to run the unit test suite before checkin and discover if you broke something   This cuts down a lot on instances of having to sit and twiddle your thumbs while waiting for someone else to fix a bug they checked in  or going to the hassle of reverting their change so you can get some work done   It s also immensely valuable in refactoring  so you can be sure that the refactored code passes all the tests that the original code did

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From my experience  unit tests and integration tests are a  MUST HAVE  in complex software environments   In order to convince the developers in your team to write unit tests you may want to consider integrating unit test regression analysis in your development environment  for example  in your daily build process    Once developers know that if a unit test fails they don t have to spend so much time on debugging it to find the problem  they would be more encouraged to write them   Here s a tool which provides such functionality   unit test regression analysis tool

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This is very  Net-centric  but has anybody tried Pex   I was extremely sceptical until I tried it - and wow  what a performance  Before I thought  I m not going to be convinced by this concept until I understand what it s actually doing to benefit me   It took a single run for me to change my mind and say  I don t care how you know there s the risk of a fatal exception there  but there is and now I know I have to deal with it   Perhaps the only downside to this behaviour is that it will flag up everything and give you a six month backlog  But  if you had code debt  you always had code debt  you just didn t know it  Telling a PM there are a potential two hundred thousand points of failure when before you were aware of a few dozen is a nasty prospect  which means it is vital that the concept is explained first

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With unit test suite one can make changes to code while leaving rest of the features intact  Its a great advantage  Do you use Unit test sutie and regression test suite when ever you finish coding new feature

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Unit Testing is definitely worth the effort   Unfortunately you ve chosen a difficult  but unfortunately common  scenario into which to implement it   The best benefit from unit testing you ll get is when using it from the ground up - on a few  select  small projects I ve been fortunate enough to write my unit tests before implementing my classes  the interface was already complete at this point    With proper unit tests  you will find and fix bugs in your classes while they re still in their infancy and not anywhere near the complex system that they ll undoubtedly become integrated in in the future   If your software is solidly object oriented  you should be able to add unit testing at the class level without too much effort   If you aren t that fortunate  you should still try to incorporate unit testing wherever you can   Make sure when you add new functionality the new pieces are well defined with clear interfaces and you ll find unit testing makes your life much easier

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Best way to convince    find a bug  write a unit test for it  fix the bug     That particular bug is unlikely to ever appear again  and you can prove it with your test   If you do this enough  others will catch on quickly

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This is very  Net-centric  but has anybody tried Pex   I was extremely sceptical until I tried it - and wow  what a performance  Before I thought  I m not going to be convinced by this concept until I understand what it s actually doing to benefit me   It took a single run for me to change my mind and say  I don t care how you know there s the risk of a fatal exception there  but there is and now I know I have to deal with it   Perhaps the only downside to this behaviour is that it will flag up everything and give you a six month backlog  But  if you had code debt  you always had code debt  you just didn t know it  Telling a PM there are a potential two hundred thousand points of failure when before you were aware of a few dozen is a nasty prospect  which means it is vital that the concept is explained first

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I m working as a maintenance-engineer of a poorly documented   awful and big code base  I wish the people who wrote the code had written the unit tests for it  Each time I make a change and update the production code I m scared that I might introduce a bug for not having considered some condition  If they wrote the test making changes to the code base would be  easier and faster  at the same time the code base would be in a better state     I think unit tests prove a lot useful when writing api or frameworks that have to last for many years and to be used modified evolved by people other than the original coders

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Unit Testing is one of the most adopted methodologies for high quality code  Its contribution to a more stable  independent and documented code is well proven   Unit test code is considered and handled as an a integral part of your repository  and as such requires development and maintenance  However  developers often encounter a situation where the resources invested in unit tests where not as fruitful as one would expect  In an ideal world every method we code will have a series of tests covering it   s code and validating it   s correctness  However  usually due to time limitations we either skip some tests or write poor quality ones  In such reality  while keeping in mind the amount of resources invested in unit testing development and maintenance  one must ask himself  given the available time  which code deserve testing the most  And from the existing tests  which tests are actually worth keeping and maintaining  See here

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A major part of test-driven development that is often glossed over is the writing of testable code   It seems like some kind of a compromise at first  but you ll discover that testable code is also ultimately modular  maintainable and readable  If you still need help convincing people this is a nice simple presentation about the advantages of unit testing

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George Stocker  Unfortunately our code base does not lend itself to easy testing    Everyone agrees that there are benefits to unit testing but it sounds like for this code base the costs are high  If the costs are greater than the benefits then why should they be enthusiastic about it  Listen to your coworkers  maybe for them the perceived pain of unit tests is greater than the perceived value of unit tests   Specifically  try to gain value as soon as possible  and not some feel-goodery  xUnit is green  value  but clean code that users and maintainers value  Maybe you have to mandate unit tests for one iteration and then discuss if it is worth the effort or not

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For years  I ve tried to convince people that they needed to write unit test for their code  Whether they wrote the tests first  as in TDD  or after they coded the functionality  I always tried to explain them all the benefits of having unit tests for code  Hardly anyone disagreed with me  You cannot disagree with something that is obvious  and any smart person will see the benefits of unit test and TDD   The problem with unit testing is that it requires a behavioral change  and it is very hard to change people s behavior  With words  you will get a lot of people to agree with you  but you won t see many changes in the way they do things   You have to convince people by doing  Your personal success will atract more people than all the arguments you may have  If they see you are not just talking about unit test or TDD  but you are doing what you preach  and you are successful  people will try to imitate you    You should also take on a lead role because no one writes unit test right the first time  so you may need to coach them on how to do it  show them the way  and the tools available to them  Help them while they write their first tests  review the tests they write on their own  and show them the tricks  idioms and patterns you ve learned through your own experiences  After a while  they will start seeing the benefits on their own  and they will change their behavior to incorporate unit tests or TDD into their toolbox   Changes won t happen over night  but with a little of patience  you may achieve your goal

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If your existing code base doesn t lend itself to unit testing  and it s already in production  you might create more problems than you solve by trying to refactor all of your code so that it is unit-testable   You may be better off putting efforts towards improving your integration testing instead   There s lots of code out there that s just simpler to write without a unit test  and if a QA can validate the functionality against a requirements document  then you re done   Ship it   The classic example of this in my mind is a SqlDataReader embedded in an ASPX page linked to a GridView   The code is all in the ASPX file   The SQL is in a stored procedure   What do you unit test   If the page does what it s supposed to do  should you really redesign it into several layers so you have something to automate

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I discovered TDD a couple of years ago  and have since written all my pet projects using it   I have estimated that it takes roughly the same time to TDD a project as it takes to cowboy it together  but I have such increased confidence in the end product that I can t help a feeling of accomplishment   I also feel that it improves my design style  much more interface-oriented in case I need to mock things together  and  as the green post at the top writes  it helps with  coding constipation   when you don t know what to write next  or you have a daunting task in front of you  you can write small   Finally  I find that by far the most useful application of TDD is in the debugging  if only because you ve already developed an interrogatory framework with which you can prod the project into producing the bug in a repeatable fashion

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Unit Testing is definitely worth the effort   Unfortunately you ve chosen a difficult  but unfortunately common  scenario into which to implement it   The best benefit from unit testing you ll get is when using it from the ground up - on a few  select  small projects I ve been fortunate enough to write my unit tests before implementing my classes  the interface was already complete at this point    With proper unit tests  you will find and fix bugs in your classes while they re still in their infancy and not anywhere near the complex system that they ll undoubtedly become integrated in in the future   If your software is solidly object oriented  you should be able to add unit testing at the class level without too much effort   If you aren t that fortunate  you should still try to incorporate unit testing wherever you can   Make sure when you add new functionality the new pieces are well defined with clear interfaces and you ll find unit testing makes your life much easier

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Make the first things you test not related to unit testing   I work mostly in Perl  so these are Perl-specific examples  but you can adapt    Does every module load and compile correctly   In Perl  this is a matter of creating a Foo t for each Foo pm in the code base that does   use ok   Foo      Is all the POD  Plain Ol  Documentation  formatted properly   Use Test  Pod to validate the validity of the formatting of all the POD in all the files    You may not think these are big things  and they re not  but I can guarantee you will catch some slop   When these tests run once an hour  and it catches someone s premature commit  you ll have people say  Hey  that s pretty cool

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Unit testing is a lot like going to the gym   You know it is good for you  all the arguments make sense  so you start working out   There s an initial rush  which is great  but after a few days you start to wonder if it is worth the trouble   You re taking an hour out of your day to change your clothes and run on a hamster wheel and you re not sure you re really gaining anything other than sore legs and arms   Then  after maybe one or two weeks  just as the soreness is going away  a Big Deadline begins approaching   You need to spend every waking hour trying to get  useful  work done  so you cut out extraneous stuff  like going to the gym   You fall out of the habit  and by the time Big Deadline is over  you re back to square one   If you manage to make it back to the gym at all  you feel just as sore as you were the first time you went   You do some reading  to see if you re doing something wrong   You begin feel a little bit of irrational spite toward all the fit  happy people extolling the virtues of exercise   You realize that you don t have a lot in common   They don t have to drive 15 minutes out of the way to go to the gym  there is one in their building   They don t have to argue with anybody about the benefits of exercise  it is just something everybody does and accepts as important   When a Big Deadline approaches  they aren t told that exercise is unnecessary any more than your boss would ask you to stop eating   So  to answer your question  Unit Testing is usually worth the effort  but the amount of effort required isn t going to be the same for everybody   Unit Testing may require an enormous amount of effort if you are dealing with spaghetti code base in a company that doesn t actually value code quality    A lot of managers will sing Unit Testing s praises  but that doesn t mean they will stick up for it when it matters    If you are trying to introduce Unit Testing into your work and are not seeing all the sunshine and rainbows that you have been led to expect  don t blame yourself   You might need to find a new job to really make Unit Testing work for you

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I do not know  A lot of places do not do unit test  but the quality of the code is good  Microsoft does unit test  but Bill Gates gave a blue screen at his presentation

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In short - yes   They are worth every ounce of effort    to a point   Tests are  at the end of the day  still code  and much like typical code growth  your tests will eventually need to be refactored in order to be maintainable and sustainable   There s a tonne of GOTCHAS  when it comes to unit testing  but man oh man oh man  nothing  and I mean NOTHING empowers a developer to make changes more confidently than a rich set of unit tests   I m working on a project right now     it s somewhat TDD  and we have the majority of our business rules encapuslated as tests    we have about 500 or so unit tests right now   This past iteration I had to revamp our datasource and how our desktop application interfaces with that datasource   Took me a couple days  the whole time I just kept running unit tests to see what I broke and fixed it   Make a change  Build and run your tests  fix what you broke   Wash  Rinse  Repeat as necessary   What would have traditionally taken days of QA and boat loads of stress was instead a short and enjoyable experience   Prep up front  a little bit of extra effort  and it pays 10-fold later on when you have to start dicking around with core features functionality     I bought this book - it s a Bible of xUnit Testing knowledge - tis probably one of the most referenced books on my shelf  and I consult it daily   link text

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Unit Testing is definitely worth the effort   Unfortunately you ve chosen a difficult  but unfortunately common  scenario into which to implement it   The best benefit from unit testing you ll get is when using it from the ground up - on a few  select  small projects I ve been fortunate enough to write my unit tests before implementing my classes  the interface was already complete at this point    With proper unit tests  you will find and fix bugs in your classes while they re still in their infancy and not anywhere near the complex system that they ll undoubtedly become integrated in in the future   If your software is solidly object oriented  you should be able to add unit testing at the class level without too much effort   If you aren t that fortunate  you should still try to incorporate unit testing wherever you can   Make sure when you add new functionality the new pieces are well defined with clear interfaces and you ll find unit testing makes your life much easier

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The whole point of unit testing is to make testing easy   It s automated    make test  and you re done   If one of the problems you face is difficult to test code  that s the best reason of all to use unit testing

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I didn t see this in any of the other answers  but one thing I noticed is that I could debug so much faster   You don t need to drill down through your app with just the right sequence of steps to get to the code your fixing  only to find you ve made a boolean error and need to do it all again   With a unit test  you can just step directly into the code you re debugging

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One of the best things about unit testing is that your code will become easier to test as you do it  Preexisting code created without tests is always a challenge because since they weren t meant to be unit-tested  it s not rare to have a high level of coupling between classes  hard-to-configure objects inside your class - like an e-mail sending service reference - and so on  But don t let this bring you down  You ll see that your overall code design will become better as you start to write unit-tests  and the more you test  the more confident you ll become on making even more changes to it without fear of breaking you application or introducing bugs   There are several reasons to unit-test your code  but as time progresses  you ll find out that the time you save on testing is one of the best reasons to do it  In a system I ve just delivered  I insisted on doing automated unit-testing in spite of the claims that I d spend way more time doing the tests than I would by testing the system manually  With all my unit tests done  I run more than 400 test cases in less than 10 minutes  and every time I had to do a small change in the code  all it took me to be sure the code was still working without bugs was ten minutes  Can you imagine the time one would spend to run those 400  test cases by hand   When it comes to automated testing - be it unit testing or acceptance testing - everyone thinks it s a wasted effort to code what you can do manually  and sometimes it s true - if you plan to run your tests only once  The best part of automated testing is that you can run them several times without effort  and after the second or third run  the time and effort you ve wasted is already paid for   One last piece of advice would be to not only unit test your code  but start doing test first  see TDD and BDD for more

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You should test as little as possible   meaning  you should write just enough unit tests to reveal intent   This often gets glossed over   Unit testing costs you   If you make changes and you have to change tests you will be less agile    Keep unit tests short and sweet     Then they have a lot of value   Too often I see lots of tests that will never break  are big and clumsy and don t offer a lot of value  they just end up slowing you down

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I recently went through the exact same experience in my workplace and found most of them knew the theoretical benefits but had to be sold on the benefits to them specifically  so here were the points I used  successfully     They save time when performing negative testing  where you handle unexpected inputs  null pointers  out of bounds values  etc   as you can do all these in a single process  They provide immediate feedback at compile time regarding the standard of the changes    They are useful for testing internal data representations that may not be exposed during normal runtime    and the big one      You might not need unit testing  but when someone else comes in and modifies the code without a full understanding it can catch a lot of the silly mistakes they might make

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Just today  I had to change a class for which a unit test has been written previously  The test itself was well written and included test scenarios that I hadn t even thought about  Luckily all of the tests passed  and my change was quickly verified and put into the test environment with confidence

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The whole point of unit testing is to make testing easy   It s automated    make test  and you re done   If one of the problems you face is difficult to test code  that s the best reason of all to use unit testing

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thetalkingwalnut asks            What are some good ways to convince the skeptical developers on the team of the value of Unit Testing       Everyone here is going to pile on lots of reasons out of the blue why unit testing is good  However  I find that often the best way to convince someone of something is to listen to their argument and address it point by point  If you listen and help them verbalize their concerns  you can address each one and perhaps convert them to your point of view  or at the very least  leave them without a leg to stand on   Who knows  Perhaps they will convince you why unit tests aren t appropriate for your situation  Not likely  but possible   Perhaps if you post their arguments against unit tests  we can help identify the counterarguments   It s important to listen to and understand both sides of the argument  If you try to adopt unit tests too zealously without regard to people s concerns  you ll end up with a religious war  and probably really worthless unit tests   If you adopt it slowly and start by applying it where you will see the most benefit for the least cost  you might be able to demonstrate the value of unit tests and have a better chance of convincing people  I realize this isn t as easy as it sounds - it usually requires some time and careful metrics to craft a convincing argument   Unit tests are a tool  like any other  and should be applied in such a way that the benefits  catching bugs  outweigh the costs  the effort writing them   Don t use them if where they don t make sense and remember that they are only part of your arsenal of tools  e g  inspections  assertions  code analyzers  formal methods  etc   What I tell my developers is this    They can skip writing a test for a method if they have a good argument why it isn t necessary  e g  too simple to be worth it or too difficult to be worth it  and how the method will be otherwise verified  e g  inspection  assertions  formal methods  interactive integration tests   They need to consider that some verifications like inspections and formal proofs are done at a point in time and then need to be repeated every time the production code changes  whereas unit tests and assertions can be used as regression tests  written once and executed repeatedly thereafter    Sometimes I agree with them  but more often I will debate about whether a method is really too simple or too difficult to unit test    If a developer argues that a method seems too simple to fail  isn t it worth taking the 60 seconds necessary to write up a simple 5-line unit test for it  These 5 lines of code will run every night  you do nightly builds  right   for the next year or more and will be worth the effort if even just once it happens to catch a problem that may have taken 15 minutes or longer to identify and debug  Besides  writing the easy unit tests drives up the count of unit tests  which makes the developer look good  On the other hand  if a developer argues that a method seems too difficult to unit test  not worth the significant effort required   perhaps that is a good indication that the method needs to be divided up or refactored to test the easy parts  Usually  these are methods that rely on unusual resources like singletons  the current time  or external resources like a database result set  These methods usually need to be refactored into a method that gets the resource  e g  calls getTime    and a method that takes the resource as a argument  e g  takes the timestamp as a parameter   I let them skip testing the method that retrieves the resource and they instead write a unit test for the method that now takes the resource as a argument  Usually  this makes writing the unit test much simpler and therefore worthwhile to write   The developer needs to draw a  line in the sand  in how comprehensive their unit tests should be  Later in development  whenever we find a bug  they should determine if more comprehensive unit tests would have caught the problem  If so and if such bugs crop up repeatedly  they need to move the  line  toward writing more comprehensive unit tests in the future  starting with adding or expanding the unit test for the current bug   They need to find the right balance    Its important to realize the unit tests are not a silver bullet and there is such a thing as too much unit testing  At my workplace  whenever we do a lessons learned  I inevitably hear  we need to write more unit tests   Management nods in agreement because its been banged into their heads that  unit tests      good    However  we need to understand the impact of  more unit tests   A developer can only write  N lines of code a week and you need to figure out what percentage of that code should be unit test code vs production code  A lax workplace might have 10  of the code as unit tests and 90  of the code as production code  resulting in product with a lot of  albeit very buggy  features  think MS Word   On the other hand  a strict shop with 90  unit tests and 10  production code will have a rock solid product with very few features  think  vi    You may never hear reports about the latter product crashing  but that likely has as much to do with the product not selling very well as much as it has to do with the quality of the code   Worse yet  perhaps the only certainty in software development is that  change is inevitable   Assume the strict shop  90  unit tests 10  production code  creates a product that has exactly 2 features  assuming 5  of production code    1 feature   If the customer comes along and changes 1 of the features  then that change trashes 50  of the code  45  of unit tests and 5  of the production code   The lax shop  10  unit tests 90  production code  has a product with 18 features  none of which work very well  Their customer completely revamps the requirements for 4 of their features  Even though the change is 4 times as large  only half as much of the code base gets trashed   25     4 4  unit tests   20  of production code    My point is that you have to communicate that you understand that balance between too little and too much unit testing - essentially that you ve thought through both sides of the issue  If you can convince your peers and or your management of that  you gain credibility and perhaps have a better chance of winning them over

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I have toyed with unit testing a number of times  and I am still to be convinced that it is worth the effort given my situation    I develop websites  where much of the logic involves creating  retrieving or updating data in the database  When I have tried to  mock  the database for unit testing purposes  it has got very messy and seemed a bit pointless   When I have written unit tests around business logic  it has never really helped me in the long run  Because I largely work on projects alone  I tend to know intuitively which areas of code may be affected by something I am working on  and I test these areas manually  I want to deliver a solution to my client as quickly as possible  and unit testing often seems a waste of time  I list manual tests and walk through them myself  ticking them off as I go   I can see that it may be beneficial when a team of developers are working on a project and updating each other s code  but even then I think that if the developers are of a high quality  good communication and well-written code should often be enough

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Unit tests are also especially useful when it comes to refactoring or re-writing a piece a code   If you have good unit tests coverage  you can refactor with confidence   Without unit tests  it is often hard to ensure the you didn t break anything

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Unit-testing is well worth the initial investment  Since starting to use unit-testing a couple of years ago  I ve found some real benefits    regression testing removes the fear of making changes to code  there s nothing like the warm glow of seeing code work or explode every time a change is made  executable code examples for other team members  and yourself in six months time    merciless refactoring - this is incredibly rewarding  try it    Code snippets can be a great help in reducing the overhead of creating tests  It isn t difficult to create snippets that enable the creation of a class outline and an associated unit-test fixture in seconds

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Unit Testing is definitely worth the effort   Unfortunately you ve chosen a difficult  but unfortunately common  scenario into which to implement it   The best benefit from unit testing you ll get is when using it from the ground up - on a few  select  small projects I ve been fortunate enough to write my unit tests before implementing my classes  the interface was already complete at this point    With proper unit tests  you will find and fix bugs in your classes while they re still in their infancy and not anywhere near the complex system that they ll undoubtedly become integrated in in the future   If your software is solidly object oriented  you should be able to add unit testing at the class level without too much effort   If you aren t that fortunate  you should still try to incorporate unit testing wherever you can   Make sure when you add new functionality the new pieces are well defined with clear interfaces and you ll find unit testing makes your life much easier

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thetalkingwalnut asks            What are some good ways to convince the skeptical developers on the team of the value of Unit Testing       Everyone here is going to pile on lots of reasons out of the blue why unit testing is good  However  I find that often the best way to convince someone of something is to listen to their argument and address it point by point  If you listen and help them verbalize their concerns  you can address each one and perhaps convert them to your point of view  or at the very least  leave them without a leg to stand on   Who knows  Perhaps they will convince you why unit tests aren t appropriate for your situation  Not likely  but possible   Perhaps if you post their arguments against unit tests  we can help identify the counterarguments   It s important to listen to and understand both sides of the argument  If you try to adopt unit tests too zealously without regard to people s concerns  you ll end up with a religious war  and probably really worthless unit tests   If you adopt it slowly and start by applying it where you will see the most benefit for the least cost  you might be able to demonstrate the value of unit tests and have a better chance of convincing people  I realize this isn t as easy as it sounds - it usually requires some time and careful metrics to craft a convincing argument   Unit tests are a tool  like any other  and should be applied in such a way that the benefits  catching bugs  outweigh the costs  the effort writing them   Don t use them if where they don t make sense and remember that they are only part of your arsenal of tools  e g  inspections  assertions  code analyzers  formal methods  etc   What I tell my developers is this    They can skip writing a test for a method if they have a good argument why it isn t necessary  e g  too simple to be worth it or too difficult to be worth it  and how the method will be otherwise verified  e g  inspection  assertions  formal methods  interactive integration tests   They need to consider that some verifications like inspections and formal proofs are done at a point in time and then need to be repeated every time the production code changes  whereas unit tests and assertions can be used as regression tests  written once and executed repeatedly thereafter    Sometimes I agree with them  but more often I will debate about whether a method is really too simple or too difficult to unit test    If a developer argues that a method seems too simple to fail  isn t it worth taking the 60 seconds necessary to write up a simple 5-line unit test for it  These 5 lines of code will run every night  you do nightly builds  right   for the next year or more and will be worth the effort if even just once it happens to catch a problem that may have taken 15 minutes or longer to identify and debug  Besides  writing the easy unit tests drives up the count of unit tests  which makes the developer look good  On the other hand  if a developer argues that a method seems too difficult to unit test  not worth the significant effort required   perhaps that is a good indication that the method needs to be divided up or refactored to test the easy parts  Usually  these are methods that rely on unusual resources like singletons  the current time  or external resources like a database result set  These methods usually need to be refactored into a method that gets the resource  e g  calls getTime    and a method that takes the resource as a argument  e g  takes the timestamp as a parameter   I let them skip testing the method that retrieves the resource and they instead write a unit test for the method that now takes the resource as a argument  Usually  this makes writing the unit test much simpler and therefore worthwhile to write   The developer needs to draw a  line in the sand  in how comprehensive their unit tests should be  Later in development  whenever we find a bug  they should determine if more comprehensive unit tests would have caught the problem  If so and if such bugs crop up repeatedly  they need to move the  line  toward writing more comprehensive unit tests in the future  starting with adding or expanding the unit test for the current bug   They need to find the right balance    Its important to realize the unit tests are not a silver bullet and there is such a thing as too much unit testing  At my workplace  whenever we do a lessons learned  I inevitably hear  we need to write more unit tests   Management nods in agreement because its been banged into their heads that  unit tests      good    However  we need to understand the impact of  more unit tests   A developer can only write  N lines of code a week and you need to figure out what percentage of that code should be unit test code vs production code  A lax workplace might have 10  of the code as unit tests and 90  of the code as production code  resulting in product with a lot of  albeit very buggy  features  think MS Word   On the other hand  a strict shop with 90  unit tests and 10  production code will have a rock solid product with very few features  think  vi    You may never hear reports about the latter product crashing  but that likely has as much to do with the product not selling very well as much as it has to do with the quality of the code   Worse yet  perhaps the only certainty in software development is that  change is inevitable   Assume the strict shop  90  unit tests 10  production code  creates a product that has exactly 2 features  assuming 5  of production code    1 feature   If the customer comes along and changes 1 of the features  then that change trashes 50  of the code  45  of unit tests and 5  of the production code   The lax shop  10  unit tests 90  production code  has a product with 18 features  none of which work very well  Their customer completely revamps the requirements for 4 of their features  Even though the change is 4 times as large  only half as much of the code base gets trashed   25     4 4  unit tests   20  of production code    My point is that you have to communicate that you understand that balance between too little and too much unit testing - essentially that you ve thought through both sides of the issue  If you can convince your peers and or your management of that  you gain credibility and perhaps have a better chance of winning them over

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Unit testing help you to release software with fewer bugs while reducing overall development costs  You can click the link to read more about the benefits of unit testing

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One great thing about unit tests is that they serve as documentation for how your code is meant to behave   Good tests are kind of like a reference implementation  and teammates can look at them to see how to integrate their code with yours

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If you are using NUnit one simple but effective demo is to run NUnit s own test suite s  in front of them  Seeing a real test suite giving a codebase a workout is worth a thousand words

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I m agree with the point of view opposite to the majority here  It s OK Not to Write Unit Tests Especially prototype-heavy programming  AI for example  is difficult to combine with unit testing

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Who are you trying to convince   Engineers or manager   If you are trying to convince your engineer co-workers I think your best bet is to appeal to their desire to make a high quality piece of software   There are numerous studies that show it finds bugs  and if they care about doing a good job  that should be enough for them   If you are trying to convince management  you will most likely have to do some kind of cost benefit reasoning saying that the cost of the defects that will be undetected is greater than the cost of writing the tests   Be sure to include intagable costs too  such as loss of customer confidence  etc

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Unit tests are also especially useful when it comes to refactoring or re-writing a piece a code   If you have good unit tests coverage  you can refactor with confidence   Without unit tests  it is often hard to ensure the you didn t break anything

User · Answer

Unit-testing is well worth the initial investment  Since starting to use unit-testing a couple of years ago  I ve found some real benefits    regression testing removes the fear of making changes to code  there s nothing like the warm glow of seeing code work or explode every time a change is made  executable code examples for other team members  and yourself in six months time    merciless refactoring - this is incredibly rewarding  try it    Code snippets can be a great help in reducing the overhead of creating tests  It isn t difficult to create snippets that enable the creation of a class outline and an associated unit-test fixture in seconds

User · Answer

If you are using NUnit one simple but effective demo is to run NUnit s own test suite s  in front of them  Seeing a real test suite giving a codebase a workout is worth a thousand words

User · Answer

I have a point to make that I cant see above    Everyone unit tests  they don t necessarily realise it - FACT   Think about it  you write a function to maybe parse a string and remove new line characters  As a newbie developer you either run a few cases through it from the command line by implementing it in Main   or you whack together a visual front end with a button  tie up your function to a couple of text boxes and a button and see what happens   That is unit testing - basic and badly put together but you test the piece of code for a few cases    You write something more complex  It throws errors when you throw a few cases through  unit testing  and you debug into the code and trace though  You look at values as you go through and decide if they are right or wrong  This is unit testing to some degree    Unit testing here is really taking that behaviour  formalising it into a structured pattern and saving it so that you can easily re-run those tests  If you write a  proper  unit test case rather than manually testing  it takes the same amount of time  or maybe less as you get experienced  and you have it available to repeat again and again

[unit-testing] Is Unit Testing worth the effort?

Examples related to unit-testing