I discovered testing and TDD when I was in university. I was trying to find something that could improve my programming skills overall and not just...
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Unsurprisingly, whether TDD and automated testing in general is useful/essential depends greatly on the task at hand. Similarly, riding your bicycle to work has a great ROI value, but using it to get a snack from the fridge, not so much 😆.
Yes, TDD is great, but only when it makes sense (i.e. don't make it into religion);
People certainly can take it too far and make it into a religion. Like it is some silver bullet that will solve all development problems when it won't. It's a technique that has its advantages and limitations, although I'd say it is one of the more useful ones I've come across. But I'm probably totally biased.
About point 2, I think it covers one of the limitations of TDD. TDD can never find an unexpected new bug in a system for a simple reason. We are the ones writing the tests, and that means that they are limited by our imagination. And, speaking for myself, we aren't very good at imagining all the ways our programs can break. We could try to stretch our imagination and write tons of tests, but then we end up with a codebase that's much harder to maintain than it needed to be. The way I found to deal with this issue is just to write enough tests to force me to implement a feature, and after the feature is "done" use exploratory testing to find bugs I didn't imagine could exist. And then write regression tests for those new-found bugs. It's been working great so far :)
I think item 1 does not consider the time spent on executing tests. When we work with software that keeps evolving during the time, writing tests makes you spend less time with tests then executing them manually every time.
There's a difference between an engineer and a hacker. One isn't better than the other, but have different values.
Applying an engineering approach to software development is impossible without test driven development, but sometimes hacking something together is where the value is.
You reminded me of a talk from Kent Beck . He expressed really well that idea that hacking and engineering can have important roles in development depending on which stage a project is at.
The Pragmatic Programmer (book) nails it:
And:
I like this perspective.
Gotta love that book. It aged really well!
Indeed. But you really don't need to be doing TDD for 30 years (or at all) to get there
TDD: absolutely fantastic and valuable if you have the skills and discipline to use it. One of the most elusive phenomena in software engineering, something of a holy grail, many people say they want it, comparatively very few actually do it (or do it well, at least).
I'm frankly still struggling to grasp how to implement tests/TDD effectively in a large, real-world application.
(More specifically, I have trouble with the idea of unit tests; functional tests fit my thinking and understanding better).
I've had a taste of how useful it can be in small side projects, but when I look at the large-scale fintech loan pricing product I develop for a client, while I can INSTANTLY see the value in having a suite of tests that will guarantee adding a new variable doesn't break the pricing algorithm, I just can't picture how to build up the suite of tests around it.
I'm also still "catching up" on general thinking around pure functions and testable code, so I'm sure that's where a lot of the problem lies for me. Poorly written code will never be effectively testable.
So all of that said, I'm working hard towards learning and using TDD.
P.S. - Don't get "comfortable enough" with what you know and stop learning and keeping up with best practices and paradigms, especially not for years "while you focus on the business side." Playing catch up after 15 years in the industry is just. no. fun.
I agree that in real-world applications, it's harder to do TDD. In my opinion, it's due to the increase in the complexity of the domain. So my strategy has been to break features down into degenerate cases that are simple enough for me to know how to write a test for them. After implementing the degenerative case, I then proceed to iterate into the next degenerate case that brings me closer to the full-fledged feature.
This example is a bit too simple, but if I have to develop a table that fetches data and has tons of sort options, my tests will probably go something like this "Shows loading while fetching" -> "Can show an error message when fetching data fails" -> "Show's message to the user if there's no data to show" -> "Can show one row" -> "Can show multiple rows" -> "Can filter rows by 'Property1' " -> "Can filter rows by 'Property2' " -> "Can filter rows by 'Property1' and 'Property2' " -> etc. Some tests might be redundant at the end of the implementation, and I'll probably delete them if that's the case. But going through this process gives me more confidence in what I'm doing and tend to lead to better tests and design.
Small steps help a lot.
Testability comes from good design and architecture, I agree.
But starting somewhere is really important. Maybe you can start with a high level test without edge cases like:
Given this input I expect this output. Add a few of them covering different code paths (delta coverage per test) and try to move forward.
That's a great observation. A lot of developers don't know how to write tests and how to write testable code. I think that a lot of that has to do with the culture of the company they're in. Especially when we're talking about project-based companies, which tend to privilege shipping as soon as possible vs. reducing the cost of development on the medium to long term, it's a kind of environment that privileges hacks over a sustained practice, which makes testing and TDD hard to flourish. So it's unlikely for someone working in a situation like that to be given the time to learn or to have someone to teach them how to test/TDD. At least, that's my experience.
I use TDD semi-regularly in my hobby projects. I've also spent the last month getting my team's main tool set up with a proper test suite. It's more for regression tests than TDD, but I'm excited about it, all the same.
I would say my experience with TDD is fairly similar - my code is better, and I think about my designs in more detail before implementing. I don't usually implement all the tests up-front, but I'll write down a large number of test synopses, and then implement the most important ones (and come back after to fill in the edge cases, just to validate my work).
I use it all the time, based on the same two points you mentioned.
Pros
For me it's the best way to implement a feature, you simply implements slowly and with a lot of confidence.
And the mais reason that i like it, is that you tend to create the feature in the most readable way.
Completely agree!
I liked how you mentioned that it lets you implement something slowly and with lots of confidence. I think it clearly expresses the feeling of being in control of the code that TDD can give.
I think sometimes TDD gets confused with ensuring good unit test coverage. True TDD means writing the tests before the actual code, something I admit I've never been a fan of or managed to get into the practice of doing. However, I am a fan of good (meaningful) test coverage, I just write tests after writing the code.
I think after a while of writing tests, you end up learning how to write code that's more testable as a matter of course.
Having test cases is important and it's useful in a DevOps perspective due to reliance on automating the small stuff which includes creating testing pipelines to test your code without you running it yourself.
As for TDD, it depends on your company or organisation engineering practices. They might require you to do it and you can do it to affect yourself. Ideally, I would go for TDD and as others have mentioned it's really subjective. Since there will be a need to write code that requires you to get it out as soon as possible. Especially you are creating a prototype or MVP who has a very short timeline for it to be completed.
How much time do you spend on writing tests?
Let's say the client asked you for a feature that will take you 1 hour to write and 2 hours to include tests. Will you charge him for 2 hours? What if the client cannot afford two hours? Will you be willing to reduce the amount of tests? (Imagine it's a question you're asked in a job interview - how critical is it for you to meet the deadline?)
I'm of the opinion of DHH, that there's a lot of test-induced damage caused by TDD.
These days I almost never write unit tests anymore, I've almost completely replaced them with integration tests, as suggested by Kent C. Dodds. As I work on the backend with Kotlin, I use test-containers to spin-up the DB, RabbitMQ or whatever, and then test the app as if it was a function (hitting an endpoint and asserting the response, for example).
One of the biggest advantages to doing this is that the tests are completely decoupled from the code (which you typically get when you use mocks), so you can refactor freely and all you have to do is run the tests to see you haven't broken anything.
When you do these sort of tests, TDD doesn't apply much anymore because you often need to connect a few components before you can actually see a result, so the "write a failing test, fix it" iterative process doesn't fit.
One question I often get when someone sees this approach for the first time is, what do you do when the system under test has a lot of variations? For those cases, I've found that a table-driven approach has always worked well. I've found that the amount of permutations you'd write if you were unit testing would pretty much be the same, if not more as some tests from other layers might overlap.
Another good article on the topic that describes well the philosophy: blog.twitter.com/engineering/en_us...
I get you. Writing tests is indeed important, I'm happy for you that all your clients can not only afford your work but also understand and value the quality of your outputs. I also appreciate the fact you clearly know how to efficiently write concise tests that give you and your client great certainty that the code won't fail. I wish all the clients would be like your clients.
If you are a very lean team trying to move quickly and progress is more important than stability then it makes no sense to spend time writing tests for code you know will radically change.
It's so frustrating to see teams trying to hit coverage numbers with useless tests. Put a value in a prop and see if the value was rendered. Lol, we've got 90% coverage with mostly useless tests that add no value, but we've got high coverage.
Projects move through different phases and high-performance teams adjust to ensure the business is supported in a way that makes the most sense for each phase.
Hi, João. I'm a code newbie and I'm still on that frustrating stage, trying to understand and implement tests in React. The concept of testing and TDD is great, but right now I don't know exactly how to get started. Do you have any recommendation for me?
For instance, do you use react-testing-library? Do you recommend a good resource for learning it (or other testing libraries)? Any hint will be really appreciated. :D
Hi Marina :)
When dealing with React applications, I tend to use Cypress, cypress-testing-library, react-testing-library, and Jest.
While knowing how to use test-related tools is a good thing, after you've learned the basics (running tests, assertions, and mocks), learning more about the tools probably won't do much to alleviate your testing/TDD frustrations, as most of them come from a lack of understanding of the goals and processes of testing/Test-driving an application.
Do you have a specific example of something that you would like to test but don't know how? I think I can give more accurate and useful hints if we go over a specific example that's causing you frustration, rather than talking about what I think is important in general when testing an application :)
Hey João, thanks for replying.
I think you are right, I'll first learn the basics of testing before diving deeper in the tools. That's where the frustration comes from, for sure.
No specific examples right now, but you answer already helped me. And I'll keep following your other articles on this subject. Thanks!
Glad I could help. Feel free to reach out if you have any particular question you think I could answer :)
I have used TDD once and find it really useful and fun to learn. I was able to write my codes more organized and easier to understand. But the thing is were not using TDD, clients wants to get things done asap.
I personally never found TDD all that helpful. It can be a great tool for providing feedback during development but it's not the only one.
With typescript + hot reloading, TDD doesn't really bring any value for me.
I also rarely write unit tests for the same reason.
I kindly disagree: The tests should not affect the implementation.
I use TDD all the time (on my job and 90% of my hobby projects) and the most I think I like about it:
the structure of the test can be completely decoupled from the structure of the implementation:
Maybe the test has 2 classes, but the implementation has 1, 2 or even 15. I always test the outside behavior of the module, never private details.
I love it when people say about TDD. I also love to use it. But I'm too lazy to do that😅
It really depends on a task, if I write something really easy, I will avoid testing at all, because I see no point at all, but if it is not the case, then It what gives me carefree attitude.
Breaking things and medium / long term maintenance are real risks. If I plan to maintain it, testing is a must.
I wouldn't do UI testing, though. I am just not convinced.
I haven't used testing in any of my projects in a 26 year professional career
That's interesting! How do you deal with regression issues when working in codebases with other people?
I don't follow TDD exactly, but for some things I do write some tests. It might not be a full on Unit Test that we are familiar with, but I usually do something to prove that what I wrote works.