Pair programming is a great way to share knowledge. But every developer is different, does pairing work for everyone?
Pairing helps a team normalise its knowledge – what one person knows, everyone else learns through pairing: keyboard shortcuts, techniques, practices, third party libraries as well as the details of the source code you’re working in. This pushes up the average level of the team and stops knowledge becoming siloed.
Pairing also helps with discipline: it’s a lot harder to argue that you don’t need a unit test when there’s someone sitting next to you, literally acting as your conscience. It’s also a lot harder to just do the quick and dirty hack to get on to the next task, when the person sitting next to you has taken control of the keyboard to stop you committing war crimes against the source code.
The biggest problem most teams face is basically one of communication: coordinating, in detail, the activities of a team of developers is difficult. Ideally, every developer would know everything that is going on across the team – but this clearly isn’t practical. Instead, we have to draw boundaries to make it easier to reason about the system as a whole, without knowing the whole system to the same level of detail. I’ll create an API, some boundary layer, and we each work to our own side of it. I’ll create the service, you sort out the user interface. I’ll sort out the network protocol, you sort out the application layer. You have to introduce an architectural boundary to simplify the communication and coordination. Your architecture immediately reflects the relationships of the developers building it.
Whereas on teams that pair, these boundaries can be softer. They still happen, but the boundary becomes softer because as pairs rotate you see both sides of any boundary so it doesn’t become a black box you don’t know about and can’t change. One day I’m writing the user interface code, the next I’m writing the service layer that feeds it. This is how you spot inconsistencies and opportunities to fix the architecture and take advantage of implementation details on both sides. Otherwise this communication is hard. Continuous pair rotation means you can get close to the ideal that each developer knows, broadly, what is happening everywhere.
However, let’s be honest: pairing isn’t for everyone. I’ve worked with some people who were great at pairing, who were a pleasure to work with. People who had no problem explaining their thought process and no ego to get bruised when you point out the fatal flaw in their idea. People who spot when you’ve lost the train of thought and pick up where you drifted off from.
A good pairing session becomes very social. A team that is pairing can sound very noisy. It can be one of the hardest things to get used to when you start pairing: I seem to spend my entire day arguing and talking. When are we gonna get on and write some damned code? But that just highlights how little of the job is actually typing in source code. Most of the day is figuring out which change to make and where. A single line of code can take hours of arguing to get right and in the right place.
But programming tends to attract people who are less sociable than others – and let’s face it, we’re a pretty anti-social bunch: I spend my entire day negotiating with a machine that works in 1s and 0s. Not for me the subtle nuances of human communication, it either compiles or it doesn’t. I don’t have to negotiate or try and out politick the compiler. I don’t have to deal with the compiler having “one of those days” (well, I say that, sometimes I swear…). I don’t have to take the compiler to one side and offer comforting words because its cat died. I don’t have to worry about hurting the compiler’s feelings because I made the same mistake for the hundredth time: “yes of course I’m listening to you, no I’m not just ignoring you. Of course I value your opinions, dear. But seriously, this is definitely an IList of TFoo!”
So it’s no surprise that among the great variety of programmers you meet, some are extrovert characters who relish the social, human side of working in a team of people, building software. As well as the introvert characters who relish the quiet, private, intellectual challenge of crafting an elegant solution to a fiendish problem.
And so to pairing: any team will end up with a mixture of characters. The extroverts will tend to enjoy pairing, while the introverts will tend to find it harder and seek to avoid it. This isn’t necessarily a question of education or persuasion, the benefits are relatively intangible and more introverted developers may find the whole process less enjoyable than working solo. It sounds trite: but happy developers are productive developers. There’s no point doing anything that makes some of your peers unhappy. All teams need to agree rules. For example, some people like eating really smelly food in an open plan office. Good teams tend to agree rules about this kind of behaviour; everyone agrees that small sacrifices for an individual make a big difference for team harmony.
However, how do you resolve a difference of opinion with pairing? As a team decision, pairing is a bit all or nothing. Either we agree to pair on everything, so there’s no code ownership, regular rotation and we learn from each other. Or we don’t, and we each become responsible for our own dominion. We can’t agree that those that want to pair will go into the pairing room so as not to upset everyone else.
One option is to simply require that everyone on your team has to love pairing. I don’t know about you: hiring good people is hard. The last thing I want to do is start excluding people who could otherwise be productive. Isn’t it better to at least have somebody doing something, even if they’re not pairing?
Another option is to force developers to pair, even if they find it difficult or uncomfortable. But is that really going to be productive? Building resentment and unhappiness is not going to create a high performance team. Of course, the other extreme is just as likely to cause upset: if you stop all pairing, then those that want to will feel resentful and unhappy.
And what about the middle ground? Can you have a team where some people pair while others work on their own? It seems inevitable that Conway’s law will come into play: the structure of the software will reflect the structure of the team. It’s very difficult for there to be overlap between developers working on their own and developers that are pairing. For exactly the same reason it’s difficult for a group of individual developers to overlap on the same area of code at the same time: you’ll necessarily introduce some architectural boundary to ease coordination.
This means you still end up with a collection of silos, some owned by individual developers, some owned by a group of developers. Does this give you the best compromise? Or the worst of both worlds?
What’s your experience? What have you tried? What worked, what didn’t?