The golden rule for this style of pairing is:
"For an idea to go from your head into the computer
it MUST go through someone else's hands"
The ProcessThis style is actually very close to an actual navigator / driver situation in a car or on a boat. With all the high level commands coming from the navigator and the lower level implementation happening from the driver.
This style of programming is all about increasing communication and collaboration. Verbally communicating code and editor commands is a skill like anything else but it is one that many people have not developed yet. Don't worry, it's pretty easy to gain and most people pick it up the basics in a few hours.
The DriverAs a driver (at the keyboard) this is a fairly simple and peaceful place to be. I have been the driver in languages and editors I was completely unfamiliar with without problem or indecent. However, there are two important things that are required for a happy driver experience.
"Trust your navigator"
When you are the driver trust that your navigator knows what they are telling you. If you don't understand what they are telling you ask questions, but if you don't understand why they are telling you something don't worry about it until you've finished the method or section of code. The right time to discuss and challenge design decisions is after the solution is out of the navigators head or when the navigator is confused and unable to navigate.
"Become comfortable working with incomplete understanding"
Even if you trust the navigator, the navigator might not be comfortable navigating you in this strong style. To combat this they might try to explain everything to you before you can actually start to code. This slows things down a lot and depending on your level of knowledge can taking hours or even days before you can even start. Don't worry about knowing everything, you will learn as you go. Don't worry about not knowing stuff. You might not know the language, os, editor, code, or even the problem space you are working in. It's ok, you will soon.
"What if I have an idea I want to implement?"Great! Switch places and become the navigator.
The NavigatorAs the navigator you have two main jobs.
- Give the next instruction to the driver the instant they are ready to implement it
- Talk in the highest level of abstraction the driver can understand
The navigator is essentially managing a ToDo list in their heads. As you go through the code you keep adding things to the list and as the driver is typing you keep removed the completed items from the list. The key is while you are handeling and tracking 2-20 things at a time, the driver is only ever responsible for 1 thing. This is the key to letting the driver stay in a state of flow. This is the number one main job for the navigator; Manage the big picture details so the driver can stay focused on the code they are typing.
The second job of the navigator is to speak at the highest level of abstraction that the driver is able to digest at the moment. This will change by driver, of course, but it will also change during the day for the same driver.
For example, a navigator might tell the the driver "extract that method" to which they might get a blank stare. The navigator should then restate that intention at a low level of abstraction. Such as "ctrl+alt+m" or even "highlight lines 14-20 and then press ctrl+alt+m". After doing that a few times the navigator should be able to revert back to the higher level of "extract that method" but always realize that later the driver might be tired or just plain forgetful, adjust accordingly.
It is the navigators responsibility to communicate in a meaningful way. This means you shouldn't be speaking above the drivers understanding. However, it is also the navigators responsibility to be ever increasing the the level of communication and understanding. Stay mindful of the driver and be constantly adjusting to them.
"Just do it"
Although you are the navigator, you are going to make mistakes and bad decisions. Correct them when you do but don't sit around and plan to try to avoid. When someone has an idea have them take the navigator role and go. once it's out look back with the benefit of hindsight and refactor or redo it so it's better.
When there are just two people, I find that often the navigator will end up with their hand on the mouse. This tend to work well when the activity is much more keyboard focused (like programing). It is horrible if you are doing something more mouse focused such as graphics or installs.
Common problems with pairing
The main reason I use this method of pairing is it solves many of the common problems I see occurring with pair programming. Here are a few of the problems and how this style of pairing addresses them.
1 person working and 1 watching
If your navigator isn't engaged then you really are not even pairing. Traditional pairing makes it unfortunately easy for the person not at the keyboard to zone out and disengage. This is literally impossible with the strong pairing style as the only way for that to happen is for both people to be doing nothing.
Fighting over the keyboard
Different people might have different ideas on how to implement something. While this still happens with strong pairing style it changes from wanting to grab the keyboard and shut out the other person to wanting to let go of the keyboard and communicate your idea to the other person.
One part of pairing that is often highlighted as a problem is the Expert/Novice combination. You can imagine that watching someone fly through pages of code when you are unfamiliar with the language, editor or even the business domain would be hard enough to follow let alone contribute. With the strong style of pairing, however, this because an very valuable combination to both the expert and the novice. In this style, the expert almost always is in the navigator position having everything go through the novice. This is a very intense way of immersion learning. I am often surprised to find how quickly I can achieve basic fluency in a language or business domain, usually within a few hours or days of being the driver.
But what about the Expert? The expert also benefits. First they are not slowed down by the presence of the novice. This is a big deal as it can be the main issue that prevents the two working together and also prevents them eventually becoming equals. The expert also benefits from being able to think at a higher level in the role of the navigator. Just as it is harder to look at a map and keep your eyes on the road as you drive a car, it is equally hard to look at the big picture problem you are solving and type the individual letters needed make compiling code. Finally, the expert benefits greatly from interacting with the 'beginner mindset'. You might have heard the saying "to really learn something teach it" and some of my most profound insights have come when a novice has simply asked me "why?"
What are you thinking?
If the thinking is happening in the same person that is typing then they usually are not talking. This means that you are suppose to guess what they are thinking through some sort of reverse engineering of the code that is appearing on the screen. By making the navigator speak out loud you help to ensure that everyone is on the same page. However, this is only the start of the benefit to talking out loud. A different part of the brain is used to talk than type. When you say something out loud a small amount of improvement occurs between your brain and your mouth (I often wish it was greater :-) There is an other level of autocorrect that occurs when it is received by the other person (I frequently find myself thanking my driver for understanding what I meant instead of what I said) but there is also a sort of 'stupid trap' where the very bad or unformed ideas are not able to bridge the gap between the navigator and driver and get flushed out because of it. Finally there is a checksum when the navigator sees the code end up on the screen. Because the navigator now has an expectation of what 'should' be appearing they are in a position to actually review that that it is what was wanted.
Just in time thinking
When the navigator gives a direction they might not know the full path of where to go. In fact, the vast majority of the time I navigate I do not know the path or even the final destination only the next step. While the driver is implementing the current step I have time to figure out the next step. In this manner the navigator can stay one step ahead of the driver the whole time.
Side Note: While this is very practical for production coding, it can sometimes lead to the misconception that the navigator knew what they were doing all the time but just didn't want to share it with the driver ahead of time.
This method of pairing has been very powerful for me and is the main way I have been pair programming for the last 11 years. It is very effective, fast and efficient.However, it can be very 'strong' as the name implies. Here are a few helpful tips I have picked up over the years to help soften it.
'ask for trust'
Sometimes the navigator and the driver will butt heads. I have often made the mistake of trying to argue the merits of my ideas when the actual problem is that the driver does not trust me. If you don't trust someone all the logic in the world isn't going to help. A simple solution to this is simply to ask for a temporary window of trust. For example:
"I know this seems wrong, but could you please trust me for 4 minutes
and then we will talk about the solution and remove it if you aren't happy"
After you get the code out there, you both will be in a place where you can now talk about the merits of it. Of course this doesn't mean you are right, you might find yourself deleting the code you just wrote but it is faster to ask for trust, program for 4 minutes and then delete it than to argue for 30 minutes to avoid ever having to write it the wrong way.
Take breaks to reflect and explain
Pomodoro's (25 minutes of code then 5 minutes walking around the block talking) can be a great way to lower the intensity of this style of pairing while increasing the shared insights and learning.
More importantly, always keep an eye out for the driver to make sure they get proper time to understand the high level picture as well. After you finish a section it can be good to stop and retrospect what just happened and ask questions.
If you are in a situation where the driver/navigator roles don't seem to change very often, it can also be good to force the roles to switch. In the short term this will slow production but it will make for a more well rounded team and have profound long term advantages.