[Code Friday] Tasty, tasty behaviour-driven development

[maradydd]

By way of sfllaw, a development paradigm I had not previously known about, and tool for developing in this fashion. Holy shmoley. I agree with Bill Tozier, I want this for Python yesterday.

Behaviour-driven development is basically test-driven development on steroids: it takes the principle we like to cite, "write your man pages first!", and hooks it right into the test-driven development cycle, except now you're developing one behaviour at a time, so you can write your tests piece by piece and have individual chunks of the system piece by piece. I like TDD, but sometimes I have to write code fast (and yes, TDD always ends up saving me time in the end, but we've all had those projects where OMG EVERYTHING IS ON FIRE AND THERE'S NOT TIME TO DO IT RIGHT. Behaviour-driven development eliminates your excuses to not do it right: you're producing code as discrete functional units, complete with tests to prove that they are correctly functioning functional units, and you're producing it fast enough to keep management/the client happy. (Clients are sometimes not happy when the first week of work goes into building the unit test suite. Yes, yes, I know, that week of work saves a month or more later on down the line. Some of my clients are no longer my clients for a reason.)

Behaviour-driven development is also a great tool for the "design the UI first" school of programming, and any project that doesn't follow that school of programming is doing it wrong. (Think of it this way: if you're writing a library, design the API first -- that is to say, write the man page first. If you're writing a web application, mock up the user interface, figure out what the damn thing's going to look like and do all your changing-your-mind about how the UI is going to behave before you start laying down AJAX requests.)

Also courtesy sfllaw, a talk by Ben Mabey explaining not only these ideas but the business decisions which motivate behaviour-driven development. This is a really great overview and I strongly encourage any programmer with a pragmatic spirit -- or, even better, an entrepreneurial one -- to block out half an hour of your time to watch it.

Alas and alack, Cucumber is not available for Python yet, and from what I've seen, I really like the way it works. It apparently can be used with PHP, but I really would prefer to avoid PHP if at all possible; my preferred style is just way too functional these days to blend well with PHP. (I've developed a thing for continuation-passing style in the last month or so.) This may end up being the thing that finally motivates me to learn Ruby. I have a little side project going on right now that has a web-application-framework-shaped hole in it, and I had been planning on using Django, but given that it's going to be a Javascript-heavy front end with likely a healthy dose of script.aculo.us, Rails could be a better tool for the job. I'll need to decide if I like how Rails talks to databases; I'm madly in love with the way Django does it and anything less will be a major disappointment, so this is definitely a factor to consider. (Current Rails devs, your input is welcome -- I know very little about your framework. I used to be cranky about the lack of integration with Apache, but there's mod_rails these days and I assume that removes a lot of the reasons I had for bitching.)

And I'd have real continuations. That's always a plus.

Decisions, decisions. But I do like the fact that tools like this exist at all; it's me who needs to get over my uncanny-valley problem with Ruby.

(karnythia, thewayoftheid, tanyad, I'm not talking about the project I'm doing for y'all, this is a different project. So many irons in the fire!)

Comments

[barbarienne.livejournal.com]

Speaking form the position of I-understand-about-one-word-in-three ignorance, I always assumed that programmers started with the UI and then worked out from there.

I mean, that seems so obviously sensible. Why would anyone do it the other way? Do they not know any people?

And then it occurred to me that this explains Windows perfectly. Light bulb!

[maradydd.livejournal.com]

I always assumed that programmers started with the UI and then worked out from there.

The world would be a better place if this were the case, but alas, no; far too much software is written from the perspective of "Algorithm Foo provides an excellent solution to Problem Bar; let's implement it! Oh, I guess we'll have to slap a UI on it to turn it into a tool..."

I am being rather generic in my use of the term "user interface"; by this I mean "whatever the user of the software actually has to touch." For a web browser, a music player, an email application, &c, this is the GUI. For a library, it's the API ("application programming interface", or set of functions which the library makes available for you to use). For a command-line tool, like 'ftp' or 'cd' or 'wget' or whatever, it's the arguments and flags that the user includes when invoking the command, and any special magic about them (cf. my brainfart last week about the ordering of libraries in an 'ld' command). For a programming language, it's the syntax of the language itself.

Another reason for things being done in clunky ways is "well, it's what people are used to, we can't just go reinvent the wheel." For all that C is annoyingly difficult to read, for instance, it's the one programming language that every competent programmer is expected to know. As such, many languages are rather C-like in their syntax, because if you know C, then you can pick up $foo fairly quickly. Java may well be replacing C, given the way that schools teach their CS curricula these days, but apart from the object-orientation and the lack of pointers, Java owes a lot to C syntax-wise as well. It's like we just can't get rid of this legacy that we don't want.