As I mentioned in my previous post, I have tremendous respect for how Pivotal Labs builds software. In this blog post, I want to cover why practices used at Pivotal Labs may not always be appropriate at other companies. The core of my argument is that Pivotal Labs is a consultancy; hence, their priorities are not always the same as the priorities for a startup building its own software.
First of all, let me talk about full-time pair programming. In the book Professional Software Development, Steve McConnell states that NASA discovered that the single most effective way to reduce defects (in manufacturing, etc.) is to always have a second pair of eyes present (i.e. to work in pairs). However, NASA must go to extreme lengths to avoid defects because lives are on the line. That's rarely the case with most startups. Most defects are merely embarrassing. In many cases, code review may be more efficient than full-time pair programming. In some cases involving purely aesthetic matters, it may sometimes be acceptable to even skip the full code reviews and settle for aesthetic reviews instead.
Full-time pair programming may also help a particular task get done faster. However, if you have a limited number of engineers at a small startup, certainly the total time to completion for all programming tasks will go down if all programming must be done in pairs. Pivotal Labs has the advantage that they can scale up the number of people on a project if a job calls for it, and they make more money when they do so. It's the opposite at a small startup. The number of programmers at a small startup is often somewhat limited and fixed, and there are economic advantages to getting more done with fewer people. If you only have two programmers, and one of them is a Ruby expert and the other an ActionScript expert, it might be best to just let them do their thing individually so that at least two things are getting done at the same time.
Don't get me wrong. I'm not saying that pair programming isn't extremely valuable. I'm just saying that full-time pair programming is extremely expensive, and sometimes the cost isn't justifiable for smaller startups that aren't consultancies.
The next thing I'd like to cover is tests. Pivotal Labs writes a lot of tests. It makes sense for them because they get paid to write them, and they never want to get caught with their pants down. If Pivotal Labs has a choice of implementing two features with a 30% chance of having a defect or of implementing one feature with a 2% chance of having a defect, they're only going to implement one feature. Since they don't get paid by the feature, they get paid the same either way.
The economics just aren't the same at a startup building its own software. Don't get me wrong--I really appreciate the value of testing, but I also try to keep in mind the cost. My approach to building software at a small startup is to consider the return on investment when writing tests. Some tests provide a very high return on investment. They catch a lot of potential bugs and require very little work. I'm thinking of high-level Cucumber and Webrat tests. Some tests require a lot of work, but don't catch very many actual bugs. I'm thinking of view tests. A view test neither tests that a view looks right, nor does it test that its interface with the controller is correct. My point is that it may be in Pivotal Lab's best interest to implement view tests, but if I'm working at a small startup that isn't a consultancy, it probably isn't in my interest to implement view tests.
So what's my point in bringing all of this up? As much as I appreciate how Pivotal Labs does things, I understand that those practices may not always be appropriate for a small startup building its own software. It reminds me of that old essay, The Rise of "Worse is Better". As much as I hate to admit it, sometimes worse is better.