Matlab xUnit DocTest transfers ownership

At a previous job, I worked a lot with Matlab. This was in 2010, before Matlab had any testing tools included, and the best testing tool was Steve Eddins’ Matlab xUnit package.

I loved (and love) the Python doctest module: it’s both a clever hack and a very useful tool. I decided to make a version of it for Matlab.

Matlab isn’t the kind of language that lets you really control the namespace of the code that is running. Python, for instance, has a nearly empty namespace by default when you run code in a separate file. R has similar capabilities, although (for me) they are clunkier to use. But, unless you explicitly make some code a function, Matlab runs it more like a script, sharing the namespace of whatever code calls it. This makes ‘doctest’ a tricky concept to implement - either you have to manipulate the documentation strings into functions, or else control the available variables very carefully.

I chose the latter route, ending up with this hilarious test-running method. I wrote it normally, and then renamed all the variables, from example_var to DOCTEST__example_var. So, the test code isn’t actually isolated, but at least it should never modify the test-running function’s state accidentally. I think, given the limitations of the language, that’s the best I could do. And it was useful. And check out the doctest on that method! Heheheh.

Anyway, the reason this comes up today is that I haven’t worked at a job with a Matlab license for several years. And GNU Octave, while probably useful for number crunching, lacks a lot of Matlab’s finer points, including its classdef classes. So I basically haven’t worked on it at all for 3 years.

But hey good news, Open Source! Mr Paul Sexton has offered to take over maintainership! I accept. That’s nice. He’s already made some changes that make the code runnable on modern Matlab versions, showing the value of having a maintainer who can at least run the code. I’m glad, and excited to see where he takes the project! Even if it’s just keeping it runnable, I expect that a few people will benefit. Good!

As an aside, I’m on the lookout for my next numeric language. I’ve had success with NumPy and Pandas, but I’ve also heard nice things about Julia. I was thinking about making doctests my first practice project in Julia, but actually, Julia doesn’t even support docstrings. Its builtins have text that’s associated with them, that shows up in help("blah"), but there’s currently no way to do that for your own code. That seems really important to me. I’ll probably stick with Python for my next vectorized-math project, though I continue to follow Julia now and then.