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Code & Supply hosted a Coderetreat focused on pair programming and test-driven development. Here’s what attendees learned

The Pittsburgh software community celebrated 12 years of Global Day of Coderetreat this weekend.

Colin Dean shares some announcements with Coderetreat participants at the start of the November 2023 Global Day of Coderetreat at Code & Supply Workspace in Pittsburgh’s East Liberty neighborhood. (Courtesy Code & Supply/Jean Lange)
This is a guest post by Colin Dean, managing director of Code & Supply. A version of it originally appeared on Leaky Abstractions' Medium page and is republished here with permission.
Code & Supply loves hosting Coderetreats.


“Coderetreats are free day-long, intensive practice events, focusing on the fundamentals of software development and design. By providing developers the opportunity to take part in focused practice, away from the pressures of ‘getting things done,’ the coderetreat format has proven itself to be a highly effective means of learning and nurturing software development skills.”

Annually since 2011, practitioners and facilitators have organized a Global Day of Coderetreat (GDCR). This is typically scheduled for the first Saturday in November nowadays, anywhere on Earth. That means it starts around noon on Friday in the US Eastern time zone and runs until Sunday at noon. This gives folks a wide time range in which to participate in a local event in person or online with folks from around the world!

Code & Supply has organized Pittsburgh’s local event since 2017 (plus 2015) and has been involved in GDCR since 2013, the year of Code & Supply’s founding. We even ran GDCR 2020 virtually, like most other events during the pandemic. (More on past Global Day of Coderetreat Code & Supply meetup events: 2015201720182019202020212022 and 2023.)

We run the event for “free” — we require a small “earnest money” payment upfront that guarantees food but is otherwise refunded, donated to Code & Supply Scholarship Fund, or donated to Code & Supply Co. to help keep the lights on at C&S Workspace, our coworking space and community center.

2023 was a great year. We remembered to take lots of pictures, including our extensive notes taken during the closing circle.

What happens at a Code & Supply Coderetreat?

Coderetreats, as Code & Supply runs, focus intensively on pair programming and test-driven development. We run a series of sessions wherein participants implement the same exercise in different languages and with different constraints. These constraints may alter the core exercise — zero-player simulation game Conway’s Game of Life — or restrict what language features you can use, require a novel testing strategy, or alter the pairing dynamic or communication.

Two people peer at a laptop on the desk in front of them.

Two Coderetreat participants, Grant and Teal, work together during a session. (Courtesy Code & Supply/Colin Dean)

One of our favorite constraints is called evil coder: One person writes tests, and the other person writes the production code. The latter writes the bare minimum code necessary to get a test to pass, even if the operations of the code are deceptive to the tester! This exercise encourages the tester to write thorough tests that carefully constrain the business logic.

Why should you attend a Coderetreat?

When you understand what participants shared during retrospectives that they learned, what surprised them, and what they’ll do differently, you’ll want to come to our next Coderetreat.

A group of people standing around a table in a room.

Participants share their learnings during a session retrospective at the 2023 Global Day of Coderetreat in Pittsburgh at Code & Supply Workspace. (Courtesy Code & Supply/Colin Dean)

What did you learn?

Some highlights:

  • How to implement and use granular tests
  • What do I actually need?
  • Prefer careful design and planning [to immediately coding]
  • Quick start templates are great for CR and general coding
  • Python dataclasses and decorators
  • GitHub Copilot [ed. a new suggested constraint for 2023 was to use only Copilot for a session; no humans writing code!]
  • IntelliJ generators for Java objects
  • C# LINQ

What surprised you?

Some highlights:

  • Rusty! Skill atrophy while working on a lot of non-code tasks makes practice like Coderetreat incredibly valuable
  • It’s fun to solve the same problem multiple times
  • I still felt productive despite working in an unfamiliar language if my partner knew it well
  • I could learn from retrospectives and apply ideas to the next session
  • I was surprised I never finished!
  • My second year was even more enjoyable than the first because I embraced process over product for the day
  • A great mix of skill levels and openness among participants enhances the exercise

And, most importantly, what will you do differently after today?

A person standing in front of a projector with a mask on her face.

Jean Lange asks during the Coderetreat closing circle with arms open, “What will you do differently after today?” (Courtesy Code & Supply/Colin Dean)

Some highlights:

  • I want to do an intra-team Coderetreat
  • I want to more often pair out of fun and curiosity than just rubber-ducking or needing help with a particular problem; to collaborate instead of extract or aid
  • I will think about coding design more deeply
  • I will use code katas more often to practice skills
  • I understand and accept “Go slow now to go fast later”

What’s next?

What will you do when you’ve gained a new perspective through practicing software development in an environment that focuses on process over product for a day?

We hope you’ll join us for the next Coderetreat next November, if not sooner. Join the Pittsburgh Code & Supply Meetup to see more events like this and be notified when we’re holding another Coderetreat event. You should also join the Code & Supply mailing list and follow us on the fediverse.

A group of people taking a selfie in front of a whiteboard.

Colin Dean, Jean Lange, Jenny Manning and Greg Hopkins. (Courtesy Code & Supply/Colin Dean)


We sincerely thank our veteran facilitators, Jean Lange, Jenny Manning, Greg Hopkins, and Colin Dean. A special shout to Code & Supply Compensation Survey Report co-author Philip Kyler for handling our logistics, including keeping us caffeinated with fresh coffee all day. Jean brought doughnuts and both Colin and Jean took pictures. We also thank Jim Hurne and Matt Fulgo for running past events.

We also thank our generous sponsors, DOT FOUNDRY and Thoughtworks employees, who wanted to ensure that we had high-quality sustenance for the event and help cover other costs. Code & Supply events discourage pizza and establish sandwiches as a baseline, but these sponsors helped us upgrade to Choolaah’s wonderful fast-casual Indian bistro.

Companies: Code & Supply

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