Fight regression

You don't want to fix the same bug several times, do you? When a bug is found, I first write a test to repeat the bug. Then I fix the code. Now every time I want to release a new version, that particular bug is tested yet again.

The 'quick fix' 5 minutes before launch

You're approaching deadline, everything is looking fine. Then, just before launch, a small bug or a tiny new feature has to be added. You can't imagine that would have side effects, can you? Well, that one bit of code, a small module that 'never changes', which you haven't looked at for 12+ months, reacts badly to this change. With good tests in place you catch this before you hit production problems.

The universe tends towards maximum irony, and you are seriously underestimating that maximum. Even with 100% test coverage, fixing something 5 minutes before launch is an awful idea. Either delay the launch, or accept that the bug is small enough to not matter.

awful idea, yes, I agree, but real world is full of awful ideas. You can either accept it and adapt, or be drowned by it.

Make refactoring easier - I quite often write tests for legacy code if I'm going to refactor it. It's the only way I can know it's still doing the same thing. Sadly, this sometimes means doing some blind (test-less) refactoring to make testing possible, but that's sometimes unavoidable... And still far better than doing the whole thing blind.

Have more confidence - I use to dread the day we pushed things live. I would actually cringe while it happened, and just wait for the shit to the fan. The more tests I have, the less I cringe and the more I enjoy the releasing of new, better code.

Can anyone tell me why they would not want to write tests? I have no biases here.

http://research.microsoft.com/en-us/news/features/nagappan-1...

What the research team found was that the TDD teams produced code that was 60 to 90 percent better in terms of defect density than non-TDD teams. They also discovered that TDD teams took longer to complete their projects—15 to 35 percent longer.

So, as with all classic engineering debates -- emacs vs vi, MySQL vs MongoDB, et cetera -- there is no definitive answer to the question should we write these tests or not? because it's an engineering tradeoff. Writing tests and then throwing them away is foolish: You wasted time. Not writing tests and then fixing 60-90% more bugs is foolish: Bug fixing is a waste of time, often wasting more time than it would have cost to avoid the bugs up-front, and risking breakages in the process.

Which waste of time is better for you? It depends on the business situation. There are situations in startups where it's not worth while to write tests. Indeed, there are situations where it is a mistake to write code at all: Use a big pile of post-it notes and a cheap outsourced worker to mock-up the system while you prove that you actually need it. Whereas once you've found your business plan the more typical mistake is to write too few tests, which is why there's a big popular movement that promotes writing lots of tests: There are more people with too little testing than people with too much testing.

You can write tests for the core algorithms and data structures but that is often only around 10%.

Some of the blur is caused by different kinds of programmer experience. We have to work with the "art" and "creativity" variable here, along with "has seen a similar pattern before". The other problem is asking the right question: What kinds of testing can create a consistent and solid improvement in acquiring money (or some other important pointy-haired boss measurement) over a 10-year period of time?

There are things that can make us feel good, nice placebos. For example, 100% test coverage is known to not equate to good, working, maintainable code: you may be missing features or doing things completely wrong, but your tests validate that your wrong thing or lack of thing is working.

Is there a magic bullet? Probably not... but it is widely believed (and probably justifiably so) that automated testing helps somehow. People will expound on the benefits. Personally, I want numbers. I want to know the pain before the tests and the less pain afterward. I want to know confidently that the time spent writing tests as part of development is less than the time spent discovering and fixing problems. Note the careful wording there.

What I really like is Selenium test that work like manual testing and I thus feel they just automate something I would need to do in any case.

At an old job, we had what was called "random testing". This was a time to relax and take a few hours to pound at the application with whatever we could think of. With luck, someone would go ahead and attempt to automate those tests. One of our favorite "random" tests was to start some complicated process and then shake the window all around the screen to see if it would crash -- sometimes it did! It forces people to rethink their threading approaches. Another fun trick is closing an app mid-processing; does it exit gracefully?

Laziness, ignorance, rapid prototyping, no budget, more important problems... all the obvious reasons. I can't think of any "good" reasons from an engineering perspective, only business.

But in my experience, even prototypes can benefit from it.

For me, testing actually makes the whole thing go faster. I spend less time worrying and more time developing, because I have the confidence that the rest of my code works exactly like I want it to.

It irks me when clients tell me how I should do the thing they're paying me to do. It seems counterproductive and is insulting.

It's a little bit like if you eat at a restaurant and you've got 20$. The cook could tell you there's something really good and way better at 50$.. but if you're happy with something less good at 15$, well, it's your body and your money. (I know that development is way different and in the long term tests will save money, but depending of the project, it's not always the case.)

('bad metaphorical thinking' Dijkstra alert)

This is wrong. If the tests pass, it is entirely possible that both the original code and the tests are faulty.

"Improving the quality of our software" is the one I tend to use, but it's so vague. How will unit testing convert into cold, hard cash is what upper management want to know.

If I am estimating how long the work will take, I am estimating how long it will take to get the functionality working correctly with X% confidence it works correctly when the product ships. Unless “X” is less than 50%, automated testing is part of writing the code, not a nice-to-have.

“Improving the quality of our code” does sound vague, kind of like arguing how many knots are permissible in a plank of wood destined or a kitchen floor. Instead, I would simply explain that these tests I write are part of writing the code, and to explain that if management want the code without the tests, they need to tell me in writing that they are ok with a confidence level hovering around 50%.

I am not kidding about this number. I may deliver code that appears to do what it is supposed to do, but my experience is that either it is broken in ways that a simple QA test doesn’t show, or somebody (somebody else or even me next week) is going to regress it between now and when the product ships. Automated tests give me the confidence that it works, works correctly, and will continue to work correctly.

Having sat through an hour long lecture on lumber grades in a scenic construction course, let me tell you, it is anything but vague.

You don't give reasons for using an ORM in your code, do you? You just do it as part of your development work. It's nothing that's being questioned by PHB's.

Writing tests is (or should be) part of your development work.

Make sure you include the time it takes to write the tests in your "time estimate".

The best you might do would be to come up with examples of people who used unit testing and things came out beautifully because of it. Things rarely turn out that beautifully without testing, so it can be pretty convincing to anyone who has dealt with software development for any length of time.

Everything else is a pleasant bonus. It amazes me that so much can be written without even touching on this.