Code Simplicity

Test-Driven Development and the Cycle of Observation

Today there was an interesting discussion between Kent Beck, Martin Fowler, and David Heinemeier Hansson on the nature and use of Test-Driven Development (TDD), where one writes tests first and then writes code.

Each participant in the conversation had different personal preferences for how they write code, which makes sense. However, from each participant’s personal preference you could extract an identical principle: “I need to observe something before I can make a decision.” Kent often (though not always) liked writing tests first so that he could observe their behavior while coding. David often (though not always) wanted to write some initial code, observe that to decide on how to write more code, and so on. Even when they talked about their alternative methods (Kent talking about times he doesn’t use TDD, for example) they still always talked about having something to look at as an inherent part of the development process.

It’s possible to minimize this point and say it’s only relevant to debugging or testing. It’s true that it’s useful in those areas, but when you talk to many senior developers you find that this idea is actually a fundamental basis of their whole development workflow. They want to see something that will help them make decisions about their code. It’s not something that only happens when code is complete or when there’s an bug—it’s something that happens at every moment of the software lifecycle.

This is such a broad principle that you could say the cycle of all software development is:

Observation → Decision → Action → Observation → Decision → Action → etc.

If you want a term for this, you could call it the “Cycle of Observation” or “ODA.”


What do I mean by all of this? Well, let’s take some examples to make it clearer. When doing TDD, the cycle looks like: Continue reading


The Purpose of Technology

In general, when technology attempts to solve problems of matter, energy, space, or time, it is successful. When it attempts to solve human problems of the mind, communication, ability, etc. it fails or backfires dangerously. Continue reading


The Secret of Fast Programming: Stop Thinking

When I talk to developers about code complexity, they often say that they want to write simple code, but deadline pressure or underlying issues mean that they just don’t have the time or knowledge necessary to both complete the task and refine it to simplicity.

Well, it’s certainly true that putting time pressure on developers tends to lead to them writing complex code. However, deadlines don’t have to lead to complexity. Instead of saying “This deadline prevents me from writing simple code,” one could equally say, “I am not a fast-enough programmer to make this simple.” That is, the faster you are as a programmer, the less your code quality has to be affected by deadlines.

Now, that’s nice to say, but how does one actually become faster? Is it a magic skill that people are born with? Do you become fast by being somehow “smarter” than other people?

No, it’s not magic or in-born at all. In fact, there is just one simple rule that, if followed, will eventually solve the problem entirely: Continue reading


Make It Never Come Back

When solving a problem in a codebase, you’re not done when the symptoms stop. You’re done when the problem has disappeared and will never come back.

It’s very easy to stop solving a problem when it no longer has any visible symptoms. You’ve fixed the bug, nobody is complaining, and there seem to be other pressing issues. So why continue to do work on it? It’s fine for now, right?

No. Remember that what we care about the most in software is the future. The way that software companies get into unmanageable situations with their codebases is not really handling problems until they are done.

This also explains why some organizations cannot get their tangled codebase back into a good state. Continue reading


The Philosophy of Testing

Much like we gain knowledge about the behavior of the physical universe via the scientific method, we gain knowledge about the behavior of our software via a system of assertion, observation, and experimentation called “testing.”

There are many things one could desire to know about a software system. It seems that most often we want to know if it actually behaves like we intended it to behave. That is, we wrote some code with a particular intention in mind, does it actually do that when we run it?

In a sense, testing software is the reverse of the traditional scientific method, where you test the universe and then use the results of that experiment to refine your hypothesis. Instead, with software, if our “experiments” (tests) don’t prove out our hypothesis (the assertions the test is making), we change the system we are testing. That is, if a test fails, it hopefully means that our software needs to be changed, not that our test needs to be changed. Sometimes we do also need to change our tests in order to properly reflect the current state of our software, though. It can seem like a frustrating and useless waste of time to do such test adjustment, but in reality it’s a natural part of this two-way scientific method–sometimes we’re learning that our tests are wrong, and sometimes our tests are telling us that our system is out of whack and needs to be repaired.

This tells us a few things about testing:

  1. The purpose of a test is to deliver us knowledge about the system, and knowledge has different levels of value. Continue reading

Users Have Problems, Developers Have Solutions

In the world of software, it is the job of software developers to solve the problems of users. Users present a problem, and the developers solve it. Whenever these roles are reversed, trouble ensues. Continue reading


The Accuracy of Future Predictions

One thing we know about software design is that the future is important. However, we also know that the future is very hard to predict.

I think that I have come up with a way to explain exactly how hard it is to predict the future of software. The most basic version of this theory is:

The accuracy of future predictions decreases relative to the complexity of the system and the distance into the future you are trying to predict.

As your system becomes more and more complex, you can predict smaller and smaller pieces of the future with any accuracy. As it becomes simpler, you can predict further and further into the future with accuracy.

For example, it’s fairly easy to predict the behavior of a “Hello, World” program quite far into the future. It will, most likely, continue to print “Hello, World” when you run it. Remember that this is a sliding scale–sort of a probability of how much you can say about what the future holds. You could be 99% sure that it will still work the same way two days from now, but there is still that 1% chance that it won’t.

However, after a certain point, even the behavior of “Hello World” becomes unpredictable. For example, “Hello World” in Python 2.0 the year 2000:

print "Hello, World!"

But if you tried to run that in Python 3, it would be a syntax error. In Python 3 it’s:

print("Hello, World!")

You couldn’t have predicted that in the year 2000, and there isn’t even anything you could have done about it if you did predict it. With things like this, your only hope is keeping your system simple enough that you can update it easily to use the new syntax. Not “flexible,” not “generic,” but simply simple to understand and modify.

In reality, there’s a more expanded logical sequence to the rule above: Continue reading


Code Simplicity, Second Revision

In June, I released a second revision of Code Simplicity. Some of you probably already know, but I thought that I should let everybody else know, too.

The most important change is that book gets into the laws and rules of software design much more quickly now. It starts with a completely re-written Preface that tells the story of how I developed the principles in Code Simplicity, and why you might be interested in them. Then it gets into a much shorter Chapter 1 that distills everything from the old Chapter 1 into a few short pages, skips the old Chapter 2 (which was a long discussion about what it means for something to be a science) and goes right into the laws.

Particularly if you’ve read the original version, I’d really love to hear your feedback on how the starting content of the new revision feels to you!


P.S. If you bought the ebook from O’Reilly, you get every new revision for free, and there will probably be even more revisions than this one! If you got the ebook elsewhere, there’s a little link inside of the book itself that will let you “upgrade” to the O’Reilly editions for pretty cheap, so that you can get this revision and every other future revision for free, too. I’m not partial to any particular method of you getting the book, but the O’Reilly editions are definitely the best way to get the new revisions as they come out.


Software as Knowledge

I don’t often dive deep into the philosophical underpinnings of Code Simplicity, but I’ve been realizing more and more that there are a few philosophical principles behind the writings that would be valuable to share. Also, some of these philosophies haven’t been fully formed until I sat with the work for a long time, applied it in a lot of situations, and talked about it with many people. This one–a theory that I have developed over time about how software can be thought of and worked with in the mind–has sort of been percolating with me for quite a while now. It’s time to get at least least part of it out on “paper,” in a blog post. So here you go:

Software is, fundamentally, a solid object that is made of knowledge. It follows all the rules and laws of knowledge. It behaves exactly as knowledge behaves in just about any given situation, except that it’s in concrete form. For example, when software is complex it tends to be mis-used. When software is wrong (i.e., has a bug), it tends to cause harm or problems. When people don’t understand some code, they tend to alter it incorrectly. One could say these things of knowledge just as one could say them of software. Bad data causes people to misbehave; bad code causes computers to misbehave. I’m not saying that computers and people can be compared–I’m saying that software and knowledge can be.

One wishes to have knowledge in a sensible and logical form. Similarly, Continue reading


Code Simplicity: The Science of Software Development

What if every software developer could gain the knowledge of long experience without having to go through the pain of repeated failure? What if, instead of being a continuous chaos of complexity and argument, the process of software development could be a sane, orderly progression that was well-understood by every single programmer involved? What if all programmers and their managers shared a common ground for discussing software development decisions–a common ground that was based on facts instead of opinion or authority, and that was actually helpful in deciding what to do on a day-to-day basis with your software project?

What if software development was a science–one with laws, rules, facts, and definitions that told you with certainty which directions to take and which directions to avoid? Not a dogmatic system which restricted you only to some particular methodology, but a series of principles that freed you to think for yourself and make the right decisions for your situation?

What if then, all of this was in a book, that book was only 90 pages long, and it was understandable by every single person working in the software industry, programmer or not? Would it make the world a different place? Find out for yourself: Continue reading