Skip to main content

PyCon: Managing Complexity (and Testing)

Managing Complexity (and Testing)

This was a talk on various metrics for code complexity.

Knowing the number of lines of code is not enough. For instance, how many of those lines are well tested? sloccount is a project to count lines of code.

The number of unittests that a project has is also not enough information.

There are many approaches to testing code coverage. For instance, do your tests test every line? Every branch? Every path? Each of these is successively harder. Even 100% path coverage doesn't guarantee you have no bugs.

Your gut feeling for how much code coverage you have is usually too optimistic.

Remember that human brains have not kept up with Moore's law ;)

He mentioned McCabe complexity as a way to measure code complexity.

Complexity != length. A function can be very long without being complex. This is the case if it has no if statements, no loops, no early returns, etc.

There is no way to test path coverage in Python.

He mentioned PyMetrics as a Python package to test code complexity. It was written by Reg Charney, a fellow member of BayPiggies.

High code complexity is correlated with a high bug count. Duh! ;)

Dead and redundant code is 40-100% more likely to be buggy.

Halstead is another metric, but the speaker said it was difficult for him to understand.

Code reviews are good.

Figleaf is a tool for testing code coverage.


Popular posts from this blog

Drawing Sierpinski's Triangle in Minecraft Using Python

In his keynote at PyCon, Eben Upton, the Executive Director of the Rasberry Pi Foundation, mentioned that not only has Minecraft been ported to the Rasberry Pi, but you can even control it with Python. Since four of my kids are avid Minecraft fans, I figured this might be a good time to teach them to program using Python. So I started yesterday with the goal of programming something cool for Minecraft and then showing it off at the San Francisco Python Meetup in the evening.

The first problem that I faced was that I didn't have a Rasberry Pi. You can't hack Minecraft by just installing the Minecraft client. Speaking of which, I didn't have the Minecraft client installed either ;) My kids always play it on their Nexus 7s. I found an open source Minecraft server called Bukkit that "provides the means to extend the popular Minecraft multiplayer server." Then I found a plugin called RaspberryJuice that implements a subset of the Minecraft Pi modding API for Bukkit s…

Apple: iPad and Emacs

Someone asked my boss's buddy Art Medlar if he was going to buy an iPad. He said, "I figure as soon as it runs Emacs, that will be the sign to buy." I think he was just trying to be funny, but his statement is actually fairly profound.

It's well known that submitting iPhone and iPad applications for sale on Apple's store is a huge pain--even if they're free and open source. Apple is acting as a gatekeeper for what is and isn't allowed on your device. I heard that Apple would never allow a scripting language to be installed on your iPad because it would allow end users to run code that they hadn't verified. (I don't have a reference for this, but if you do, please post it below.) Emacs is mostly written in Emacs Lisp. Per Apple's policy, I don't think it'll ever be possible to run Emacs on the iPad.

Emacs was written by Richard Stallman, and it practically defines the Free Software movement (in a manner of speaking at least). Stal…

JavaScript: Porting from react-css-modules to babel-plugin-react-css-modules (with Less)

I recently found a bug in react-css-modules that prevented me from upgrading react-mobx which prevented us from upgrading to React 16. Then, I found out that react-css-modules is "no longer actively maintained". Hence, whether I wanted to or not, I was kind of forced into moving from react-css-modules to babel-plugin-react-css-modules. Doing the port is mostly straightforward. Once I switched libraries, the rest of the port was basically:
Get ESLint to pass now that react-css-modules is no longer available.Get babel-plugin-react-css-modules working with Less.Get my Karma tests to at least build.Get the Karma tests to pass.Test things thoroughly.Fight off merge conflicts from the rest of engineering every 10 minutes ;) There were a few things that resulted in difficult code changes. That's what the rest of this blog post is about. I don't think you can fix all of these things ahead of time. Just read through them and keep them in mind as you follow the approach above.…