Spotlight – Episode #2

Exercism and 99 Bottles of OOP

with Katrina Owen at OSCON London 2016

All Episodes

Welcome to the first Spotlight series recorded at OSCON London 2016. Jerod talked with Katrina Owen, an accomplished speaker, creator of the excellent coding practice and feedback site,, and the co-author of 99 Bottles of OOP. Have you ever heard the story of how Katrina went from anonymous developer to sharing a byline with Sandi Metz? She shared all the details during this face-to-face chat.



OSCON – O’Reilly’s Open Source Convention combines the experience of the open source community with ideas and strategies for using open source tools and technologies. There’s no event quite like OSCON! Make plans now to be at OSCON May 8-11, 2017, in Austin, TX. Registration is now open — save 20% on most passes by using the code CHANGELOG20 when you register.

Notes & Links

📝 Edit Notes

  • The Changelog #225: 99 Practical Bottles of OOP with Sandi Metz - Adam and Jerod talk with Sandi Metz about her beginnings on the mainframe, her 30+ years of programming experience, the ins and outs of OOP, her book Practical Object-Oriented Design in Ruby (aka POODR), as well as her latest book 99 Bottles of OOP which she co-authored with Katrina Owen. We also covered a few listener submitted questions at the end.
  • The Changelog #202: 23 Years of Ruby with Matz (Yukihiro Matsumoto) - Adam and Jerod talk with Matz, the creator of the Ruby programming language, about where he began as a programmer, the origins of Ruby, its history and future, Ruby 3.0, concurrency and parallelism, Streem, Erlang, Elixir, and more.
  • Exercism — Level up your programming skills
  • Practical Object-Oriented Design in Ruby (POODR) - is a programmers tale written by Sandi Metz, explaining object-oriented design (OOD) using realistic, understandable examples. POODR is a practical, readable introduction to how OOD can lower your costs and improve your applications.
    about how to write object-oriented code.
  • 99 Bottles of OOP - a book by Sandi Metz and Katrina Owen written as a practical guide to writing cost-effective, maintainable, and pleasing object-oriented code.
  • Therapeutic Refactoring - a story about taking complicated, untested code and changing it in small, safe steps to make it easier to understand. It walks through the step-by-step process of adding characterization tests, as well as working through a classic refactoring, “Replace Method with Method Object”.


📝 Edit Transcript


Play the audio to listen along while you enjoy the transcript. 🎧

[00:31] Welcome to our first Spotlight series, recorded at OSCON London 2016. I’m Jerod Santo, managing editor of Changelog. Katrina Owen is an accomplished speaker, creator of the excellent coding practice and feedback site, and co-author of 99 Bottles of OOP.

Have you ever heard the story of how Katrina went from anonymous developer to sharing a byline with Sandi Metz? She shared all the details during this face-to-face chat. Listen in.

* * *

As I told you, we had Sandi Metz on the show recently, which was kind of like a checkbox, like a bucket list for us. We always have to act like we’re cool about it… You know, we had Matz on a year ago, sweatin’ bullets… Like, it’s Matz! And he was nervous, which made us nervous… But on that one we just were like, “You know what? We’re just gonna grovel. [laughter] We don’t have to play it cool, we’re gonna just tell you how awesome you are over and over again.”

Yeah, because that’s not awkward…

I know, right? He was very gracious, and a great guest, and amazing story… Do you know his story…? He never had access to compute power, so he just read about programming languages.

No, I didn’t know this.

He had one computer, but it could only do - and I’m gonna botch the details - Turbo Pascal, or something…


So he would just do that. But then he would go to the library and he’d buy books about Lisp and about these other languages…

That’s amazing.

I don’t think Perl was a thing back then, but probably SmallTalk and these things… And he would just read books about programming languages, and then he would kind of have this wanderlust, or this desire… He thought they were so beautiful, but he never used them. So by the time he was adult and doing things, he had this super knowledge of all these different design constructs and decisions, because he read the decision-making process and he thought about it, but he never got to use the practical ramifications of the decisions, and that kind of inspired him to create Ruby.

So he told us that story, and it was just amazing. But with Sandi we tried to play it cool, and even she seemed a little bit nervous, even though she talks now for a living. Then a few minutes later she was over it, and everything was good.

Yeah, Sandi’s an amazing speaker. I first heard about her – well, I stumbled across a video that she did, a conference… This is way before her book, so nobody knew… Basically, she knew whoever was at the local meetups; that’s the thing that you do when you work as a minion at some university or whatever. So she had done a talk at Gotham Ruby or something like that, and I stumbled across it on the internet and it was amazing. At the very end, someone was asking, “So, do you blog? Do you write?”

She’s like, “I don’t do anything.”

And she was like, “Oh, I know I should, but I don’t… But I’m working on this book, but it’s not gonna be ready for a long time.”

[laughs] Did you meet her then?

No, so the timestamp on this video was a year earlier, and she said “Oh, the book won’t be ready for at least a year”, and I was like “Where’s the book!? It must be ready!” So I found it in beta on Safari Books Online; I tried to buy it and there was a bug on the website that they wouldn’t take my money…

So you couldn’t get it…?

I complained on Twitter, I was like “Safari Books Online, you need to take my money because I need this book”, and then Sandi came across it and she was like, “Um, let’s figure out how we can make this happen.” So I got to read the beta.

You really wanted that book.

[04:03] Oh, my goodness! It was really exactly what I needed at that time. I had been struggling with refactoring and trying to figure out on my own, like “How do you make code better? How do you remove dependencies? How do you make it more readable? How do you make it less painful?” The talk was all about that; it was like exactly that, and this book was gonna be life changing.

You just knew it.

It had to be. And then I was right too, because it was amazing.

That’s awesome. You were right. So you kind of busted onto the scene giving a talk, and then you got on Ruby Rogues because of the talk, kind of…

Very much because of it. I lived in Oslo, I knew 12 people; we’d go to the same meetup every month. I worked at a product company that was really cool there; small, like there were seven or eight engineers. And there was a conference that was announced in Sweden for the summer, and I hadn’t really been to a conference before, and I wanted to do that. So I was like, “Hey, CEO person, who has money and control, can I go to this conference?” He was like, “That sounds like a great idea, you should go to this.”

Ask and you shall receive.

Yeah, and a couple of my colleagues came along as well. I met all of these amazing people in the Ruby conference (it was a Ruby conference)… These fantastic people, who were welcoming and friendly and interesting and interested… I was a nobody and I was still having these fantastic conversations with people.

At one point, a couple other guys were like, “You should give a talk.” I was like, “No… Hah, that’s not gonna…”

Yeah, that’s what everybody thinks at first.

That’s not even gonna happen. Like, when would I do that? How would I do that? What would I talk about? Nothing, right? And then a year later I applied to give a talk at that same conference.

Well, what changed your mind, though? Because you said, “No, no, no”, and now later you’re doing it.

So one of the guys said, “It’s really challenging, and it’s really worth it.” And I was like, first of all the fact that he acknowledged that fact that this is really hard - that was a relief. That made me think, “Okay, so he’s not pretending it’s easy.” Hard things - I know how to do hard things: you practice. You work really hard and you figure our what the rules are, and then you practice.

Yeah, you put in the effort, and…

So I was like, “Um, maybe I could do that”, but I put it away… I kept going to these meetups in Oslo, and every meetup I’d bring a little refactoring that I had done; I wouldn’t show it upfront, but when most of the people had left, I’d pull it up and then say, “Oh, look what I did! This was a fun refactoring.”

And people liked it.

Yeah, somebody said, “I would watch a whole talk of this.” I was like, “Oh, I could do a talk.”

Nice! So that was like a little bit of a confidence boost. You have to try. Was this the talk that shocked the Ruby world?

Yeah, totally. [laughter] It brought down Twitt– no…

Twitter was going down pretty easily back then.

That’s true, there was a fail well going on…

It was a low bar.

The bar was very low… No, so I did this talk, and James Edward Gray of the Ruby Rogues saw a video of it, and was like, “You should all see this talk, it’s really good”, and then they invited me on the show to just talk about refactoring. Then later they brought me back on as a panelist.

I recall that, because I used to listen to Rogues back then, and James was so effusive about this talk that I was like, “I should just pause this and go watch, I guess.”

It’s fascinating… I was so terrified when I was gonna give this talk. I thought I was gonna throw up, because I was just so scared. I had no idea what the reception would be.

What do you think that – first, for the audience’s sake, let’s lay out what the talk was, but then tell me what you think really resonated about it. Because it did. Everybody loved it - why?

[07:53] Yeah, so the title was Therapeutic Refactoring. The CFP was blind; first of all, I was given a chance, even though I had no experience speaking, nobody knew anything about who I was. The abstract spoke for itself, and the title I think was alluring. This conference was also at a spa…

It was at a spa?

It was at a Japanese spa in Sweden?

Talk about therapeutic, right? You were so on theme.

Right, so I think I totally lucked out, in some ways. The talk itself was a very straightforward, simple story… But it really was a story. I formed it as “There’s this horrible code and it’s untested. How do you deal with it?” So it was the process, step-by-step, of adding characterization tests, and then the process (step-by-step) of refactoring. And it was using one of the recipes from Martin Fowler’s Refactoring book; I hadn’t made anything up.

Right, you were just applying something that you read.

Yeah, and applying it sort of gently and carefully. And the whole point of the talk was that refactoring is something that can make you smarter, because it offloads a lot of the irrelevant details out into your tests, and this process, which is like lots of tiny steps, so you don’t have to hold as much in your head; you’re freeing up cognitive resources, and it makes you feel better and happier… So it’s worth doing.

So it was therapeutic, yeah. So that happened, that was a thing…

Yeah, and I think the thing that resonated was that it was told as a story. It’s not a readme; I’m not reciting a readme. They could go read a blog post, but it might not feel the same.

Yeah. So I’m just now thinking about your journey a little bit, because here you were, kind of stalking Sandi Metz’s Safari page, trying to get her book…

No kidding, yeah… Sandi Metz, who at the time was completely unknown, which is almost ridiculous to think about now…

And then your internet fame explodes because of the talk, Sandi’s does because of the book…

Yeah, and she’s way more famous than I am.

…and then she starts giving talks.

Her fame - she can’t even go to the restroom if she goes to a conference, because she’s being mobbed by the hoards who want to talk to her.

But you wanted to read her book so bad, and then a few years later you’re writing a book with her. That’s kind of a cool reversal…

Yeah, it is a cool reversal. I’m trying to think what were the steps in that. So the first thing was I gave her a ton of feedback about the book. After reading the first chapter, I was so excited that I sent her feedback, and she was like, “Oh, could you do that more? Could you just put your stream of consciousness in the margins?” I was like, “Yeah, I could totally do that.”

So I did, and when I finished doing that, we got on a call and talked about…

And a friendship probably spawned, or a relationship spawned.

Yeah, in some way… We had things to talk about, and it was an interesting – I think we both got something out of that. And this is just about the time where my talk got accepted (Therapeutic Refactoring), so…

Okay, so it was pre-Therapeutic Refactoring.

She gave me feedback on the early versions of the talk, and the most important feedback - there were a couple of really important things that she… My talk would have been worse than mediocre is she had not had given me some pointers.

And they were…?

The first bit of feedback was I showed her the before and after shot of the first refactoring – I had like seven examples that I was gonna put in this talk, and she was like “That’s enough for ten talks. Let’s just go with one example.”

I see… So focus it in, and don’t try to do too much.

Don’t try to do too much. And then I showed her the before and after and sort of explained, and she was like, “Okay, so now you look smart and I feel dumb…” I was like, “Oh, that’s not good…”

[11:54] That’s not the goal, right?

That’s not what I was trying to go for, so I worked really hard to try to figure out how do I carry the audience along with me in this discovery, so that it really feels like this is… I mean, this is not hard, right? But I want you to understand when watching it that this is simple and it’s approachable and it’s something that you can do, and it’s not magical; I’m in no way special for doing this. So that was really important.

Then she said, “You’ve gotta tell a story”, and I was like “How do you do that?” She was like, “You just do…” [laughter] This is something that some people have been doing all their lives, they tell stories, and that’s never been something that I had done, so I started reading books about storytelling; The Anatomy of a Story is a book that is written by a screenwriter, and it’s pulled in Hollywood films where the script isn’t going to the right place… They bring him in to save a project.

Nice, that’s a good one.

Yeah, so I just started reading as much as I could to try to understand how do you structure a talk in order for it to be compelling, and stuff like that. Over time we just had things to talk about.

Right. Then POODR got released, and she continued to give talks.

And I continued to give talks…

Rinse and repeat…

Rinse and repeat… I launched Exercism.

That got on Wired.

That got on Wired, I was terrified.

It took you to a new level.

Oh, my goodness. Yeah, so the thing about Exercism that’s important here is that Sandi in the very beginning did some of the exercises, sort of just for her own edification, and one of those exercises was the 99 bottle of beer problem…

Oh, no way!

…which kicked off this whole thing where we went off, each to our own side, to do a bunch of refactoring, and we’d get on a call and say, “Why did you do this? I hate that/I love that. That’s interesting. Hm… I’m not sure I understand where you’re going with that…”

Right. To round that out a little bit… So the book is 99 Bottles, that you guys worked on together, and it’s all about a specific problem. When we had Sandi on the Changelog we talked to her like “Why is that problem so profound? Why is it perfect for this style of teaching and all those things?”, and she gave a lot of reasons. But what I didn’t ask is where did it come from?

After the call, I was like “I should have found out…” – like, “Did you think of this? Were you just like, ‘No, it’s gonna be good’, or did you stumble upon it?” It turns out it was a part of Exercism.

It was a part of Exercism…

Mind = blown.

…and people had been submitting solutions to this problem and they were all kind of terrible, and at some point…

So where did you get it?

Let’s see… I probably – I mean, there’s a whole website of 99 Bottle of Beer in all the programming languages.

Oh, there is? It’s kind of like Fizz-Buzz, or something.

Right, yeah. I think it was also used as one of the exercises in Chris Pine’s Learn To Program book, so it’s been out there. It’s one of those common things that’s got just enough algorithmic complexity to be useful.

But it looks simple.

Ridiculously simple.

Everybody thinks immediately, “Oh, I can do that in like ten minutes.” And you can…

And you can…

But not well. [laughs]

Well, you can do a simple version, but nobody wants to do a simple version. They all wanna do a clever version.

They want people to think, “You’re smart and I’m dumb.” [laughter] Okay, so you introduced her to that problem via Exercism, and you both would kind of solve it in your own ways…

Well, in particular Sandi was solving it in really interesting ways. When most people submit a solution to Exercism, they’ll submit one solution and then you talk about that. She submitted one solution that had four solutions in it; four completely different approaches with this long commentary of like, “Well, if this were the tradeoffs I was making, then this solution… But if this other thing, then this other solution.” It was the most interesting approach that I’d ever seen in terms of not what the actual solutions were, but in terms of thinking deeply about the design tradeoffs here. Like, in what situations would one approach/design work, and in what situation would another?

[15:58] Also, this sort of lead to me asking, “There are these abstractions in this problem - how did you know?” and she was like, “Well, I just did.” And I couldn’t see it.

Eventually, over time, we used my refactoring practice and skill to figure out how can we go step by step from the simple solution to these abstractions that she just knew were there, because of her experience.

She had the expert intuition, or the experience, where you just don’t.

That’s an awesome skill, but it’s not a helpful skill for other people.

It’s really hard to teach…

And you had the refactoring history and practice of going step-by-step, so together you helped her kind of unfold how she got there. She would jump from step one to seven, but you were like, “Let’s document two, three, four, five and six.”

Yeah, and I didn’t quite understand the process that I used. It’s lots of tiny steps, but I didn’t necessarily understand – there, as well, was this element of like “I just did it in a way that I couldn’t really articulate the value of.” And of course, when she first saw it, she was kind of horrified, because it was like “Why would you do such a thing? Why don’t you just do the thing that’s kind of obvious?” I was like, “Well, it’s not obvious to me…”

It’s only obvious to a certain eye. Tell me about the book writing process now… What was that like? She sends you stuff, you send her stuff? How did that work?

So we worked on the problem back and forth for a long time, until we started realizing what the actual lessons in it were - both refactoring and design lessons - and then people were hounding her to give courses, to teach classes… Privately, in businesses, publicly as well, but mostly private. So we got together and worked out sort of an early version of some curriculum that we could go teach together, and we would prep in the morning, debrief in the evenings…

Of course, our first plans were nothing like reality, but over time things settled into a rhythm. We understood what the curriculum was… After a while, we had seen and heard every single version of every single…

There’s not a solution that could possibly surprise you guys, right?

Right, after a while…

…for the 99 Bottles.

Yeah, I’m pretty sure we’ve seen it all. So the curriculum got tightened up, and after a while - I don’t even know at what point we’ve decided this, but this kind of has to be a book. We understand the content, we understand the problem really well, we’ve taught it, we’ve seen all of the objections, we’ve seen all of the solutions, we should be able to turn this into a book.

At that point, we worked a lot on the structure of the book. We had all of the code examples step by step by step, and it was like, “Okay, what is the structure in terms of chapters and sections? In which order do we put all of these ideas?”, and then finally, there’s like a final actual writing pass which Sandi does for having a very consistent voice in the whole book. And then several rounds of editing.

So is it out there? Is it done?

It’s out there, but it’s not done…?

Yeah, so it’s in beta. It’s six long chapters, so it’s a proper-sized book, like hundreds of pages; I don’t know what the size is right now, but that number is probably available on our website.

She said there was like 45,000 words at one point.

Yeah, I think that was the four chapters.

Yeah, that’s a lot of words.

So the first five chapters out of six are out. We didn’t want to release it – we released the first four chapters in beta this summer (early June, early July, something like that). We didn’t wanna release it before those four chapters – before we had something that you could actually read and get something out of it. We didn’t want to sell you a promise, we wanted to sell you something concrete, that has valuable, that will be more valuable, but that you can already enjoy.

[20:05] That’s a great story. I hope it’s a really good book. I was able to sit in a little bit on one of your trainings, so I understand the problem and I have a feeling that it’s gonna be a really good book, because just walking through the refactorings of that specific problem… I was there working for the Changelog, not taking the class, just observing, but I wanted to bust out my editor…

Oh, it’s so tempting…

It was compelling. It was very compelling. And even as a person who’s done object-oriented for ten years, I was just like, “This is a somewhat transformative way of applying thought to code.”

Yeah, the actual ideas in the book are very simple, but it’s hard to – that simplicity that’s at the other side of complexity that some people talk about… You have simple that’s kind of naive, and then you have this complexity that feels very satisfying, and getting beyond that complexity is really hard, but once you do, you get to these deeper, simpler truths, and I think that that’s something we’ve managed to do with this book.

Yeah, very cool. Let’s talk about conferences a little bit, because it’s kind of been a launchpad for you, at least in your public career. Here we are at a conference, OSCON… You used to be scared and had to step out on the ledge to give a talk; over time, you’ve probably now done talks many times, you’ve been to all the conferences all over the world… I’m sure conferences are different now than they were before. I know you’re here with GitHub so you’re kind of working as well, but you’re speaking… What do you try to get out of conferences nowadays?

The most important thing is meeting people, having real conversations. Not those fleeting, “Oh, hey… What do you do? I program. Me too! We have so much in common!”, but to actually be able to say, “Oh yeah, you work on this project - what’s hard about it? What’s interesting about it?” Those conversations are really valuable. They don’t always, but they often grow into something that’s a little bit more durable. Now there’s this face that I recognize, this voice that I know, this person that I have some/very little idea of what they care about, so suddenly on the internet when I see tweets from them or blog posts from them I have this bigger idea of who this person is.

Right, a more round picture of people.

Yeah, and I think that’s a valuable thing, because suddenly these tenuous relationships become important in other ways. It’s like, “Oh, we suddenly are going to be working on a very similar thing, and I have experiences and you have experiences, and we can trade, and it’s gonna be useful.”

There’s a lot of people that go to conferences and they find that getting past the shallow, “Hi, how are you?”/shake the hand, it’s very difficult. You’re a quiet person, you’re kind of shy, and yet you seem to have relationships with conferences - maybe because just because you do it so much, and because you’ve been to so many… But do you have any tips? How do you bust out of that awkwardness, that fear, or whatever it is that keeps us from even engaging in conversations and conferences? You just go to the talks, and then go back to your hotel room.

Well, going to the talks is good, but it’s kind of the least valuable part of a conference.

Especially when they record them and put them online… You can watch it later.

That, too. So the talks are interesting in particular because they can work as a conversation starter; you meet someone at the coffee stand and you’re like, “Wow, what have you seen?”

Yeah, it’s a shared experience.

Yeah, and then that’s a launching point for trying to find that common ground where you can actually have a real conversation. Often, those real conversations happen in that edge of where technology meets human fear.

I like that.

[24:03] You’re now talking about the vulnerability of being human and not being perfect, and not figuring this all out, and that’s often where we can help each other in just having insights and sharing experiences.

I would say it’s worth it. It’s worth stepping out a little bit. I have a tendency where if I have a lot of knowns in the place, I will just cling to them.


I always had friends in high-school or college, we’ll go to a party, and if I have three buddies with me I’ll just hang out with them the whole time.

Yeah, I see people do that at conferences. I think it’s a shame.

Well, I kind of do, too. I kind of like coming to this conference by myself, because I don’t really have a choice - I’m either the awkward one, standing by himself, or I go talk to somebody. So it kind of pushes me over my tendency to cling to the known, because there’s no known here to cling to, which is kind of cool.

Well, this has been a lot of fun. Closing thoughts, words of wisdom?

No, I’m not wise.

[laughs] You heard it here first - Katrina Owen, not wise. Check out 99 Books – I keep calling it 99 Books…

99 Bottles of OOP.

I call it 99 Problems, I called it 99 Books… 99 Bottles of OOP - check that out. Thanks for stopping by here at OSCON.

Thanks for having me!

* * *

Thanks again to our friends at O’Reilly for the awesome working partnership at OSCON London 2016. We’ll see you again, OSCON, in 2017 in Austin, Texas. If you want to save some money on that ticket, if you’re going, use the code “changelog20” to save 20% off your registration to OSCON 2017 in Austin, Texas.

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