A year of mob programming, part 2: Collective Code Ownership

With respect to a team assigning tasks to developers by their function (frontend, backend, infrastructure, and so on), mob programming fosters Collective Code Ownership.

This is more in the sense that everyone should be able to contribute through the mob in any area, rather than everyone being able to prioritize on their own what needs to be improved. The pact is that our time belongs to the team, and the team decides what is important.

A result of this is an healthy prevention of knowledge silos, where you can exercise your own creativity just because no one else knows how to work in that area anymore.

Code review happens continuously in the mob on small changes, and there are no huge feature branches to go through. In large changes such as those, it's too late for review to suggest a valuable but completely different approach; there is too much investment of time and energy into code. If review dares to suggest groundbreaking changes, it causes extensive rework instead.

There is a larger picture on ownership: team members tend to keep track of what they care about, whether that is consistency in architecture, front end approaches to styling, performance issues, and so on.

Sometimes I found myself being talked out of a design I had in mind, counteracting bias I could have for the first or most familiar solution. I started working on this team with an object-oriented mindset, but we have transitioned to functional programming in TypeScript.

Sometimes, there are hills to die on: hard to reverse decisions on architecture, or programming language choices. It's a job of a psychologically safe team to discuss these choices collectively without drama or oversimplification like JavaScript being the the death of computer science. 

"I told you we should have written the code in English, not Latin!"

It tooks three different iterations to get a repeatable pattern for accepting Commands (as in CQRS). But it was more fruitful to focus on the Domain Events design, as a difficult choice to revisit, than on the shape of the code itself which can be refined at any time.

Working outside of the mob

The counterpart to the XP mantra of writing all production code in pairs (or a mob) is to allow team members to contribute when they are working alone due to other necessities, such as an unstable Internet connection or a flexible day where they can't align completely with the core hours of the team.

I have learned to ask the team to be commissioned something to do, or at least to give them a choice. This keeps the prioritization in the hands of the group, again reducing bias.

It's helpful to assign problems that have only a constrained possible solution such as renaming, or propagating a refactoring through the codebase for consistency's sake.

It also helps to report back what you have learned during a solo coding exercise when rejoining the mob; unexpected issues or decisions you had to take on the spot and you feel unsure about.

You're allowed to stop at a certain point, as making progress alone at all costs is valued less than maintaining collective code ownership and a shared understanding of how our application works.

Technical spikes can also be chosen by a single person to work on, either because they want to individually prioritize them to demonstrate an idea; or because the amount of investigation required makes it difficult or frustrating to collaborate.
Spikes can be built on throwaway branches, being optimized for learning rather than for delivering production quality code. Once an idea has been demonstrated and approved, the mob can implement it pretty quickly on the trunk, and if we believe in the practice, with an higher level of quality. I constantly find feature branches worked by a single person to be a dead end (especially if they are my own).

In the end, people are frequently in meetings, researching or even just on holiday for a given day. Hence there's always someone missing that will catch up on the progress when they come back into the mob. But the group itself never stops even as the components change, so some of that progress will happen every day, other things being equal.

Stay tuned for the next part of this post, A laboratory for team dynamics.

Image by Johann Jaritz.