The TDD That Can be Spoken Is Not the Eternal TDD

Reading time ~12 minutes

For all the talk on the interbutts about TDD and related topics, it sure seems like as a working programmer I run into a startling amount of projects – a great majority, really – that either have no tests, or have old useless tests that were abandoned long ago; and a startling number of developers who still don’t write any tests at all, let alone practice a TDD style of work. It’s as if as an industry we’re all putting up a big front about how important testing and TDD is to us but then when the fingers hit the keyboard, it’s all lies. That’s probably not really the case, but rather that test-infected developers are a small but vocal minority – that developers that test tend to also be the kinds of developers that blog, make podcasts, present at conferences, write books, and so on, but these happen to only be a sadly small percentage of all the developers out there cranking out code. But this minority has been talking about testing for what, a decade now at least? So why hasn’t the portion of developers seriously testing grown faster?

Once you’ve got going with TDD or even just a little automated testing, and have come to rely on it, one of the most frustrating things is to find yourself having to collaborate with others who have not, and have no interest in it. You really don’t want to leave an only partly-tested system, meanwhile these other developers on your project will make changes that break your tests with impunity. The path of least resistance is to fall back in line with the rest of your team and go back to what one of my professors back at UNI referred to as the “compile-crap” cycle – a loop of add or change some code, try to compile it, say “crap” when fails, repeat – except for interpreted languages, substitute in place of the compile step, running the application and trying to “use” it, so maybe call it the “run-crap” cycle. This friction may well be one of the biggest factors slowing the adoption of TDD; but the less developers are testing, the more it will happen, so it’s also an effect. It’s a vicious feedback loop.

Then there’s maintenance, and/or working with “legacy” code, without tests, or with bad tests. Many a project is written with no tests ever – just banging out code in a run-crap loop.

Others start out with tests, but somewhere during the development process something changes and the team reverts back to run-crap. Why do they do this? It may be that members of the development team have been swapped out for some, shall we say, ahem, “cheaper” ones; this might happen when the product is launched and comes to be seen as in “maintenance” phase, but it also happens earlier on. Or it may be that the developers reverted to comfortable old habits in the face of schedule pressure from management – after all TDD can be slower in the short-term, especially when you’re new at it, and it’s easy to lose focus on careful discipline in favor of short-term speed (or at least the appearance thereof) when the management is breathing down your neck or freaking out at you.

In any case, the eventual result is either no tests, or tests that are no help because most of them are failing because they express requirements that have since changed – which might be even worse than no tests at all; it can look like the best way to deal with it is to just nuke the whole suite.

But then what? Touching on how TDD informs design, it’s well established that code written without TDD is likely to contain design that is much harder to write tests for, with lots more coupling and dependency snarls. As requests for bug fixes and new features come in for such a system, how do you work on it in a test-driven manner? Stopping the world long enough to retrofit a complete suite of difficult-to-write tests isn’t feasible and chances are there’s no documentation you can consult when you hit all those ambiguities in what some code should be doing, so you’re likely not to even know what exactly to test for – the definition of “legacy code” as being that for which requirements have been lost. Practicing TDD on greenfield projects is relatively obvious; but the vast majority of development time is spent in maintenance, and legacy/maintenance is “advanced” TDD. I’m probably not telling you anything you don’t already know. Michael Feathers’ book Working Effectively With Legacy Code is the authoritative source on the subject, but if it’s not feasible to halt work long enough to Test All The Things, then is it feasible to halt work long enough to read a book, especially if you’re a painfully slow ADHD-stricken reader like myself? Yet again, it’s much easier to go back to the good old irritating-but-familiar run-crap loop.

It’s clear that as an industry we only stand to benefit by spreading the good word of TDD far and wide. The more it’s being done, the better. But the factors I’ve just outlined present very real obstacles to its adoption. It’s a long-term project of raising awareness and educating the developer public. Meanwhile, what can you as an individual developer do? For starters, if you really want to do TDD but are stuck in a job where everyone’s oblivious to the concept, it’s probably not worth your time trying to force that kind of sea change on your own. You’re swimming against a torrent. My advice? Find a company that’s as serious about it as you are, and go work there instead.

I myself don’t even consider my work to be test-driven. I’m a believer in TDD, and I make the best, sincerest attempts at it I can relative to the time and energy constraints within which I am working. I certainly don’t consider myself an enlightened TDD guru. I even come out and say just that right in the introduction to my résumé. What’s that, you’re supposed to talk yourself up in a résumé and make yourself sound like the answer to all a company’s prayers so that you get the job? I don’t believe in that. I’m hoping to score a gig working with test-driven developers but I don’t want to be expected to be perfect at it from day one if such a company hires me; I want such a job because I know I have a lot to learn and am looking for advantageous situations in which to learn. It pains me that such honesty should seem radical, but in my experience, the pains that come from getting oneself into the wrong situations are worse.

Developers can also tend to be a prickly lot with a healthy distrust of dogma. And sometimes the practices of what I might call “strong” or “pure” TDD can feel like a dogma, especially when delivered in a kind of hellfire-and-brimstone way a la your average Bob Martin conference talk. I don’t care for the idea that you cannot be considered a professional developer if you don’t practice TDD (and by whose standard/definition of TDD anyway?).

As I have begin to view it, TDD isn’t something you just start doing and are able to do all of it flawlessly from the get-go. Among the many concepts and tools you’ll need in order to be able to completely test-drive all parts of a system, there’s things like the delicate art of mocking, how to fake a logged-in user, how to make a unit test truly isolated, how to mock a collaborator without making the test useless, what different kinds of tests there are, and a lot of subjective experience-based intuition about what tools and techniques are best suited for what kinds of tests and situations. It can all feel really daunting.

Especially in the context of a web applications, and then especially when you’re working with a framework such as Rails, there’s a big learning curve, one that I think would be better viewed as a long process of continual improvement. There will be difficulties along the way, but in the meantime you still have to get work done and people are still paying you. To say you can’t call yourself a professional until you’ve already mastered every aspect of TDD feels, frankly, insultingly elitist. You have to crawl before you can walk before you can run before you can fly. Doing some testing still beats the pants off not doing any. I don’t think agile development processes was ever meant to be dogmatic. The processes should be flexible, adaptable, pragmatic – just like the code you hope to write when you use TDD to guide the design.

The problem so far is that too seldom is TDD presented in this way. Instead it’s usually framed as, you’re either TDD or you’re not. (And by the way what constitutes TDD is a constantly moving target.) That way of looking at TDD isn’t going to help you or anybody else adopt it. All it does is feed into your impostor syndrome.

I think it’s worth reminding oneself that guys like Corey Haines took years to get that good at a totally test-driven style. I mean just watch that video. He’s test-driving every little piece of a Rails application totally outside-in, that is, starting with the “outermost” layers, what the user sees, the GUI, the views, and working inward towards the hard candy database center. There are so many points where he shows techniques for isolating the piece he’s working on, hacks to circumvent the coupling inherent in Rails’s architecture in order to get Rails to let him keep working at an upper level of the application instead of bombing out with an error about some lower-level piece not existing yet. Techniques that I just don’t think I would be able to absorb by rote, that he seems to have arrived at on his own through leaps of intuition and experience that I don’t see myself being able to duplicate. It’s quite beautiful but even though I know he wants to sell these videos, I concluded that this wasn’t going to work for me. We all gotta find our own way, I guess.

That kind of outside-in TDD approach is very much in-vogue right now, though. And another thing that’s very in-vogue at the moment, and a very useful guiding concept, is the Rails Testing Pyramid. The tl;dr of it is that your unit tests are the most important, and should be the type of test you have the most of; and as you look up the Rails stack each kind of test is slower and more integrated and rests on the foundation of those below it.

The mosaic of types of tests you might use in a Rails application is larger than they present in that article, and I think several of them can be grouped together in the “service tests” category, but you can see approximately where they would live in the pyramid relative to each other – in order starting from the bottom: unit tests, model tests, controller tests, request tests, helper tests, view tests, client-side/javascript tests (which might be a whole other pyramid actually), and finally acceptance tests/features. As you go up the pyramid in this way too, you find that the tools and techniques become more advanced in skill, or at least are usually assumed to be and presented as such: testing literature usually begins with unit tests, and Rails-oriented testing literature usually begins with what the Rails community have traditionally called “unit tests,” which are tests at the model layer, which might be integrated with related models and might be tied to the database, or might be totally isolated from both, depending on how well you’ve gotten the hang of the higher-level skills of mocking and isolating from the database.

But here’s what I realized a while ago: when you put the outside-in approach together with the Rails Testing Pyramid, the implication is that you are building a pyramid top-first.

Does that even make sense? I mean, I realize we’re talking about software here, not big blocks of stone. It’s a metaphor, but I think there’s useful insight to be gotten from metaphors. The Agile and XP literature says so too.

You’ve got a pyramid of your own to build: your repertoire of testing skills. And if building a pyramid it top-first seems counterintuitive, building all of it at once certainly should.

All your favorite TDD gurus had to have started somewhere – probably with a few simple unit or model tests just like most of us probably did. If you get too attached to an ideal of TDD enlightenment, it can be discouraging. Better to keep TDD in mind as a guiding principle, an ideal, then just start testing. As you progress, keep a sharp eye on ways to get more test-driven – places where more testing, new kinds of tests, new techniques and tools, can help you be more confident in your code with more ease. Tackle learning those as you feel yourself become ready for them.

I recently had this idea for a presentation that would bring together concepts from Testivus with a sprinkling of Buddhist philosophy. The saying “if you meet the Buddha on the road, kill him” seemed prescient, but I wouldn’t want to be misinterpreted as advocating anyone’s murder.

I think it can be pretty easy to sell developers on some kind of automated testing. There’s a big win right away in that you can spend more time writing useful code versus less time filling out the same web form over and over like a trained monkey. That’s already going to make you more productive and your day more enjoyable. Traditionally the introduction to testing has been at the unit test level, but I almost wonder whether it would be better, now that there are good tools for it, to start from full-stack acceptance tests right away and go as far with that as you can. You may end up with slow, very coarse-grained tests this way (and it’s for this reason that so many testing advocates will tell you it’s wrong), but at least they will exercise most of the system and you will catch defects and regressions you were likely to miss otherwise. Of course any developer/team working in this way will end up experiencing some pain when the test uncovers a bug but can’t pinpoint where in the system it is originating; but that’s a good pain point to have if it can be turned into a motivation to dig into those deeper levels of testing.

Convincing developers to test shouldn’t be as hard as it looks like it’s been made. It’s time to simplify the pitch: Testing is a path to reduce suffering. You will be learning it forever.

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