August 12, 2014
TDD is TDD (And Far From Dead)Now, it would take enormous hubris for me to even suggest that this blog post that follows is going to settle the "What is TDD?" "Is TDD dead?" "Did weazels rip my TDD?" debates that have inexplicably sprung up around and about the countryside of late.
But it will. (In my head, at any road.)
First of all, what is TDD? I'm a bit dismayed that this debate is still going on, all these years later. TDD is what it always was, right from the time the phrase appeared:
Test-driven Development = Test-driven Design + Refactoring
Test-driven Design is the practice of designing our software to pass tests. They can be any kind of tests that software can pass: unit tests, integration tests, customer acceptance tests, performance tests, usability tests, code quality tests, donkey jazz hands tests... Any kind of tests at all.
The tests provide us with examples of how the software must be - at runtime, at design time, at tea time, at any time we say - which we generalise with each new test case to evolve a design for software that does a whole bunch of stuff, encompassed by the set of examples (the suite of tests) for that software.
We make no distinction in the name of the practice as to what kind of tests we're aiming to pass. We do not call it something else just because the tests we're driving our design with happen not to be unit tests.
Refactoring is the practice of improving the internal design of our software to make it easier to change. This may mean making the code easier for programmers to understand, or generalising duplicate code into some kind of reusable abstraction like a parameterised method or a new module, or unpicking a mess of dependencies to help localise the impact of making changes.
As we're test-driving our designs, it's vitally important to keep our code clean and maintainable enough to allow us to evolve it going forward to pass new tests. Without refactoring, Test-driven Design quickly becomes hard going, and we lose the ability to adapt to changes and therefore to be agile for our customer.
The benefits of TDD are well understood, and backed up by some hard data. Software that is test-driven tends to be more reliable. It tends to be simpler in its design. Teams that practice TDD tend to find it easier to achieve continuous delivery. From a business perspective, this can be very valuable indeed.
Developers who are experienced in TDD know this to be true. Few would wish to go back to the Bad Old Days before they used it.
That's not say that TDD is the be-all and end-all of software design, or that the benefits it can bring are always sufficient for any kind of software application.
But it is very widely applicable in a wide range of applications, and as such has become the default approach - a sort of "start for ten" - for many teams who use it.
It is by no means dead. There are more teams using it today than ever before. And, as a trainer, I know there are many more that aspire to try it. It's a skill that's highly in demand.
Of course, there are teams who don't succeed at learning TDD. Just like there are people who don't succeed at learning to play the trombone. The fact that not everybody succeeds at learning it does not invalidate the practice.
I've trained and coached thousands of developers in TDD, so I feel I have a good overview of how folk get on with it. Many - most, let's be honest - seriously underestimate the learning curve. Like the trombone, it may take quite a while to get a tune out of it. Some teams give up too easily, and then blame the practice. Many thousands of developers are doing it and succeeding with it. I guess TDD just wasn't for you.
So there you have it, in a nutshell: TDD is what it always was. It goes by many names, but they're all pseudonyms for TDD. It's bigger today than it ever was, and it's still growing - even if some teams are now calling it something else.
There. That's settled, then.
Posted 5 days, 22 hours ago on August 12, 2014