Wednesday, November 28, 2012

Announcing my Bachelor's thesis: Mock library for MATLAB

After positive experiences blogging about my GSoC projects, I've decided to do the same for my Bachelor's thesis. I've always felt that writing helped me process and refine my thoughts, and I'm hoping to leverage this for my thesis. Therefore, I plan on writing regularly, even about failed approaches.

As the title suggests, my thesis will be about creating a library for Mock objects for MATLAB. During talks with my mentor, we concluded that, while a unit-test library for MATLAB exists (xUnit) there is no support for mock objects. Mocks are very useful as they allow developers to write robust, correct tests faster, so their lack in MATLAB can be felt. As MATLAB supports object-orientated programming, we are reasonably certain that Mocks can also be implemented. Thus, the first part of my thesis is to conduct a feasibility study and develop a simple prototype as a proof-of-concept. To do that, I would need to define exactly which features I am looking for.

Coming from a Python background, my first instinct was to check existing Python Mock libraries (from this nice list). Most of them are ports of existing mocking frameworks to Python, though there are varieties. What was more interesting to me is that there is actually quite a bit of confusion about terminology (in particular, the term "mock" is used to refer to objects of vastly varying complexity). Investigating this, I came across an excellent article by Martin Fowler, Mocks Aren't Stubs. The article is a great read throughout, as it goes into quite a bit of detail on "mocking" and general design issues; it also made me realize that most approaches are quite complicated. Taking a step back, it's fair to assume that the "average" user of MATLAB isn't a dedicated CS specialist, but rather a researcher. As such, I believe ease of use should be valued the highest, otherwise no one would take the time to learn these tools.

This approach led me to mockito (nice presentation on differences between mockito and other frameworks, slides 38-40 provide direct comparisons of code). mockito defines itself as a "Test Spy" framework, where a "spy" is in essence a stub which remembers which interactions were invoked on it. This is a very natural, light-weight approach which is easy to pick up and almost as powerful as more verbose frameworks. After discussing it with my mentor, we both agreed that basing the new framework on mockito is the right approach. The next course of action is to create a basic set of use-cases, based on existing mockito examples, and start implementing them. This first code will be strictly proof-of-concept.

Finally, one of the first decisions we made was to make the final, resulting code public; development will also probably happen on Github. Philosophically speaking, I would prefer that any work I do be actually useful, and the idea behind creating a library is for many people to use it, and that cannot be accomplished in the confines of a single faculty or university. It would also be useful to have some projects which would like to use Mocks, so that the library can be tested (and designed!) with real code in mind. Here I would like to turn to the community - if someone has felt a need for a similar library, please send me your desired use-cases and any other comments and ideas you might have. They would be a tremendous help!