Henrik Warne

JUNE 19, 2022

I recently finished Effective Software Testing – A Developer’s Guide by Maurício Aniche , and I really liked it. I have been coding for a long time and I think I have been writing pretty good tests for the features I have implemented. Even so, I found this book quite valuable. Particularly the chapters on how to systematically come up with test cases based on the specification, inputs, outputs and the structure of the implementation.

Software Review 223

Software Review Testing Systems Review Technical Review 223

Henrik Warne

DECEMBER 13, 2021

There seems to be an established truth in programming that code reviews find a lot of bugs. An example is chapter 18 (Modern Code Review ) in the book Making Software. This is however not my experience – I rarely find outright bugs when reviewing changes. But I still think code reviews are useful. Below are my thoughts on the value of code reviews, and how to make the process efficient.

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Software Review Weak Development Team Testing Programming 201

Henrik Warne

JULY 12, 2021

I really liked A Philosophy of Software Design by John Ousterhout. It is compact and short, only 170 pages, so it is a quick read, but it contains many good ideas. The focus is on how to structure systems to make them easy to understand and work with. The author is a professor of Computer Science at Stanford, but he has also spent 14 years developing commercial software.

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Software Review Systems Review Software Examples 255

Henrik Warne

JUNE 15, 2021

I used to think that I didn’t need comments if I wrote self-documenting code. However, I have realized that I do write comments, and that I find them really useful. To see how many comments I write, and what kind they are, I wrote a script to analyze my git commits from the last six years. In total, seven percent of my committed lines contained a comment.

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Analysis Examples Programming Testing 361

Henrik Warne

MAY 23, 2021

Microservices have gone through a complete hype cycle. From being hailed as the one true way to build systems, to a backlash where they are often considered too difficult and complex. In a way though, they are like most technology – there are trade-offs. You get some benefits and some drawbacks. Here are four features specific to microservices that I have come to appreciate.

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Microservices System Network Examples 137

Henrik Warne

APRIL 18, 2021

For the past few months, I have been interviewing with several companies. In all cases, one or more coding tests were included. I have also been on the interviewing side, evaluating a coding test. Here are my thoughts on the process. Are coding tests needed? When I started out as a software developer, nobody did coding tests as far as I know. You just talked to the hiring manager for an hour, and if they liked you, you got an offer.

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Software Review Software Development Testing Recruiting 249

Henrik Warne

APRIL 15, 2021

Here are more good programming quotes I have found since my last post. Programming. “It has been said that the great scientific disciplines are examples of giants standing on the shoulders of other giants. It has also been said that the software industry is an example of midgets standing on the toes of other midgets.” Alan Cooper. “Changing random stuff until your program works is bad coding practice, but if you do it fast enough it’s Machine Learning.” via @manisha

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Programming Machine Learning Artificial Inteligence Examples 220

Henrik Warne

DECEMBER 27, 2020

Choosing test values when writing unit tests is mostly guided by the need to cover all cases of the program logic. However, some values are better than others. Here are a few tips on how to pick values that make mistakes easy to spot and the tests easy to read. Plus a bonus tip on a quick way to double check your tests. . 1. Make mistakes obvious. Suppose you have a function that subtracts one number from another, then using 20 – 10 = 10 is not so great.

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Testing Insurance Examples Programming 296

Henrik Warne

NOVEMBER 25, 2020

This fall I took the course Mathematical Modelling of Football from Uppsala University. It was taught by Professor David Sumpter , and I believe this is the first academic course of its kind. The main subjects covered are modelling and analysis of events (on the ball actions), movement and pitch control (tracking data), player evaluation, and match result simulations.

Software Review 138

Software Review Course Games Systems Review 138

Henrik Warne

AUGUST 30, 2020

You have developed a new feature. The code has been reviewed, and all the tests pass. You have just deployed this new feature to production. So on to the next task, right? Wrong. Most of the time, you should check that the feature behaves as expected in production. For a simple feature it may be enough to just try it out. But many features are not easily testable.

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Software Review Systems Review Testing System 240

Henrik Warne

JULY 23, 2020

To check if a program is doing what it should, you can inspect the output from a given input. But as the system grows, you also need logging to help you understand what is happening. Good log messages are crucial when troubleshooting problems. However, many developers don’t log enough information in the right places. I look at logs when I troubleshoot a problem.

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Software Review Systems Review Metrics Examples 255

Henrik Warne

JUNE 9, 2020

Because of the Corona pandemic, our whole company has now been working from home for 12 weeks. Before, we mostly worked in the office, although occasionally people would work from home, for example when waiting for a delivery. This abrupt switch has made for a great natural experiment on the differences between these two ways of working. Many developers on both Twitter and Hacker News argue that remote work is the future, and that they want to keep working remotely even after the need for it bec

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Weak Development Team Video Meeting AWS 164

Henrik Warne

MAY 19, 2020

I really enjoyed reading Artificial Intelligence – A Guide for Thinking Humans by Melanie Mitchell. The author is a professor of computer science and an artificial intelligence (AI) researcher. The book is her attempt at working out if the singularity is near (or at least likely), or if we still are far from creating any true intelligence. In the process, the reader gets an excellent overview of the state of the art in areas such as image recognition, game play, and natural language proces

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Artificial Inteligence Artificial Intelligence Systems Review Software Review 330

Henrik Warne

APRIL 26, 2020

In the fall of 1999 I got the biggest productivity boost of my entire career as a software developer. In the October issue of IEEE Computer magazine, there was an article by Kent Beck called “Embracing change with extreme programming” In it, he outlined Extreme Programming (XP), which includes much of what we now refer to as agile development.

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Agile Software Development Testing Programming 187

Henrik Warne

MARCH 22, 2020

I really like Secure by Design. The key idea is that there is a big overlap between secure code and good software design. Code that is strict, clear and focused will be easier to reason about, and will have fewer bugs. This in turn makes it less vulnerable to attacks. This is easy to say, but Secure by Design is full of techniques for how to actually do this.

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Examples Hotels Insurance Testing 264

Henrik Warne

JANUARY 19, 2020

Here are more good programming quotes I have found since my last post. Microservices. “Microservices are just dynamic linking over HTTP” via @mononcqc. “kubernetes – turning things off and on again, at scale” @decimalator. Full stack. “A full stack developer is just one function call away from a stack overflow developer.” @brainsmoke. dev 1: I’m full stack. dev 2: pop. dev 1: f**k.

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Programming Microservices Machine Learning Artificial Inteligence 33

Henrik Warne

JANUARY 4, 2020

In the book club at work, I just finished reading Grokking Deep Learning by Andrew Trask. It is an introduction to deep learning, but there are some problems. It spends a lot of pages on the basics, and in the end moves on to some fairly advanced topics. It is also contains many small and irritating mistakes. However, it does have some great insights into deep learning.

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Henrik Warne

DECEMBER 8, 2019

A few weeks ago I spoke at the EuroSTAR software testing conference in Prague. The conference had one and a half days of tutorials, followed by two and a half days of talks. Around a thousand people attended. I was impressed by the sense of community and by the number of activities offered. For climate reasons, I chose to travel there and back by train instead of flying.

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Conference Testing Travel Weak Development Team 26

Henrik Warne

OCTOBER 27, 2019

I really enjoyed Classic Computer Science Problems in Python by David Kopec. It covers many different problems I hadn’t read detailed explanations of before. For example: neural networks, constraint-satisfaction problems, genetic algorithms and the minimax algorithm. Unlike many other books on algorithms and programming problems, this one builds up complete (but small) programs that are easy to explore on your own.

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Programming Network Training Machine Learning 20

Henrik Warne

SEPTEMBER 29, 2019

I like to use Test-Driven Development (TDD) when coding. However, in some circumstances, TDD is more of a hinderance than a help. This happens when how to solve the problem is not clear. Then it is better to first write a solution and evaluate if it solves the problem. Writing tests only makes sense after the solution is viable. Last week, I came across examples of where I developed new functionality without using TDD.

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Software Review Systems Review TDD Test-Driven Development 170

Henrik Warne

SEPTEMBER 15, 2019

I often get contacted by recruiters asking if I am interested in changing company. Even if I am happy where I am, I briefly check out companies I have not heard of before. One reason is that you never know, maybe the new company is a fantastic opportunity that really is interesting to me. Another reason is that I don’t know how things will change – maybe I will want to change in a year’s time or so.

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Recruiting Software Development Software Review Company 76

Henrik Warne

JULY 27, 2019

What a great book Designing Data-Intensive Applications is! It covers databases and distributed systems in clear language, great detail and without any fluff. I particularly like that the author Martin Kleppmann knows the theory very well, but also seems to have a lot of practical experience of the types of systems he describes. There is so much to learn for me in this book, so I have summarized the main points from each chapter, with a special emphasis on what I found most interesting.

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Systems Review Software Review Applications Data 214

Henrik Warne

JUNE 15, 2019

At the end of May I attended Nordic Testing Days in Tallinn, Estonia. It was the first time I spoke at a conference outside of Sweden, and I had a great time. There was one day with tutorials, and two days with workshops and regular half hour talks. Here are my impressions: Talks I Liked. Why Should Exploratory Testing Even Be the Subject of a Keynote?

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Testing Conference Quality Assurance Microservices 100

Henrik Warne

MAY 26, 2019

The book Accelerate details the findings of four years of research on how DevOps affects various outcomes, such as software delivery tempo and stability, as well as the organizations’ profitability and market share. DevOps in this context means things like continuous delivery, automated tests, trunk-based development, and proactive monitoring of system health.

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Software Review Systems Review Weak Development Team DevOps 109

Henrik Warne

APRIL 3, 2019

I like good programming quotes. Here are some new ones I have found since my last posts. Complexity. “Why do people find DNS so difficult? It’s just cache invalidation and naming things.” – @jdu. “Your code doesn’t work!” “It works on *my* machine.” “Fine, we’ll ship your machine!” And that’s how Docker started.

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Henrik Warne

MARCH 30, 2019

Is programming like math, or is it like writing? I think there are elements of both in it, even though programming is a discipline of its own. Nevertheless, it is interesting to think about what aspects are like math, and what aspects are like writing. Maybe it will even lead to a better understanding of what programming is. Like Math. Sometimes, the domain of the program requires math, for example machine learning, graphics programming or financial modelling.

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Programming Exercises Machine Learning Artificial Inteligence 162

Henrik Warne

DECEMBER 2, 2018

For the system at work, I am on call one week every seven weeks. For most of the past ten years, I have been on organized on call rotations for the systems I have been developing. I think being on call is a logical way of taking responsibility for your work. You also learn a lot from it. However, it is stressful and an inconvenience, so you should get payed for it.

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Development System Games Examples 224

Henrik Warne

AUGUST 11, 2018

I use a shell every day. Almost always, I want to repeat a previous command, or repeat it after a slight modification. A very convenient way is to use arrow-up to get the most recent command back. Another common trick is to type ctrl-r and incrementally search for a previously used command. However, there are two other tricks for repeating previous commands that I use all the time, which are not as well known.

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Testing Games Resources Examples 108

Henrik Warne

MAY 28, 2017

Many software developers have a tendency to avoid talking to people. They would rather just rely on written communication in chats, email or issue tracker tickets. However, talking to people more can make them more effective as software developers. Here are some examples: Example 1. Suppose you are implementing a new feature. The ticket in the issue tracker describes how the new functionality should work.

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Henrik Warne

JULY 10, 2017

Last week I attended a software development conference, QCon in New York. Here are my impressions of it, as well as some thoughts on programming conferences in general. For me, there are several reasons to attend developer conferences. You have a chance to hear what is going on in the field of software development – what are the new techniques and technologies other companies are using.

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Conference Programming Software Review Technical Review 100

Henrik Warne

AUGUST 20, 2017

I recently found out about the book Developer Testing – Building Quality Into Software by Alexander Tarlinder , and I immediately wanted to read it. Even though I am a developer at heart, I have always been interested in software testing (I even worked as a tester for two years). I think the subject of the book, developer testing, is timely. There seems to be a broad trend where more and more responsibility for testing is given to developers.

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Testing Development Software Review Systems Review 116

Henrik Warne

SEPTEMBER 16, 2017

A good programming quote captures an insight about programming, often in a funny way. Many quotes are quite famous, but I like ones that are a bit less well-know. A while ago, I listed some favorites. Here are more good quotes I have found since then. Enjoy! Programming. “What one programmer can do in one month, two programmers can do in two months.” – Fred Brooks (maybe). “Hardware eventually fails.

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Programming Hardware Software Data 131

Henrik Warne

NOVEMBER 19, 2017

During my career as a software developer, I have seen the release frequency increasing steadily. When I started, it would take 12 to 18 months for new features to reach the customer. Years later the frequency increased, so deployment to production happened every three weeks. For the past two years, we have been using continuous delivery at work. This means that as soon as a feature is ready (implemented, code-reviewed and tested), it is deployed to production.

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Continuous Delivery Software Review Systems Review Testing 174

Henrik Warne

NOVEMBER 26, 2017

It is now more than 6 years since I started blogging about software development. It has been a great experience, and I thought I would reflect on what I have learnt. So here are my reasons for writing about programming, a bit on my process, and some statistics. Why. Knowing what I think. Formulating or explaining something in writing makes me think it through really carefully.

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Programming Software Review Software Development Course 105

Henrik Warne

DECEMBER 17, 2017

For the past two months, I have been helping my son’s grade 8 class to learn to program. All students wrote Python programs and got a feel for what programming is. This post has details on how we organized the course, code examples and lessons learned. Background. This year, all schools in Sweden are required to start teaching programming. Many schools already teach programming, but they depend on having teachers that know enough to teach.

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Programming Games Course Examples 149

Henrik Warne

MARCH 13, 2018

In the book club at work , we recently finished reading Exercises in Programming Style by Cristina Videira Lopes. The book consists of a simple program implemented in 33 different programming styles. It is a great way of showing the different styles, and the book was quite popular in the book club. The book is relatively new (it was published in 2014), and I don’t think it is as well-known as it deserves to be.

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Exercises Programming MVC Software Review 179

Henrik Warne

MAY 1, 2018

For the past few years, I have heard many people advocating using only automatic tests. For example, if all the automatic tests pass, then the code should automatically be deployed to production. I have always performed a bit of manual testing before feeling confident about my code. So for the past year I have paid extra attention to bugs I have found manually testing my own code.

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