A while ago Steve invited me to give a short presentation at one of a series of workshops he's running. These 'Reftest' workshops are aimed at bringing academia and industry together to share our insights and experiences with both Test Driven Development and Refactoring.
There were too many interesting presentations at last week's event for me to describe them all. But they should all eventually end up on the Reftest website so you can read them there. That site doesn't have a feed yet so I've set up this: http://www.google.com/notificationservice/webchanges/webfeeds/11897478376600010732 which basically notifies you of any changes to the website.
Anyway, there was a lovely presentation by Charles Tolman from Quantel about some of the issues you run into when you have a 12 year old codebase containing 17 million lines of C++ and Python. This lead into an interesting discussion about detecting duplicate code. I maintain Same but nowadays I find that Eric Raymond's Comparator is a better solution for most people so I recommended that.
One of my favourite asides from Charles's 30 years in software (20 of them spent at Quantel) was "tools should enable the intelligence of the programmer rather than attempt to encapsulate the intelligence of the programmer."
The folks from the University of Kent showed some impressive results for their tools which provide:
- model checking
- property-based testing
- interactive clone elimination
Best of all many of the principles behind them aren't restricted to Erlang. So these kinds of techniques and tools can be applied to mainstream languages. They just chose Erlang because the tools were built as part of the ProTest project they're doing with Ericsson.
My own presentation looked at some of the problems with TDD and Refactoring.
I discussed problems with teaching the cluster of tacit knowledge that we call TDD and covered issues like the convenient fictions we use, the mis-leading tutorials and the overly simplistic examples that involve starting with a blank slate. I also threw in a brief digression about the Norvig-Jeffries kerfuffle.
The section of my presentation on refactoring mostly involved going back to Opdyke's thesis and looking at some of the consequences of his ideas. One thing that struck me was how insightful Opdyke's work was when it came to the issues like preserving class invariants and the subtle side-effects of most refactorings. Somewhere along the line though as we automated refactoring we seem to have lost the heart of his ideas.
I'd expected the last section with it's references to model checking, property-based testing tools like ScalaCheck, mutation testing and fuzz testing to be controversial but the discussion ended up being a very productive look at ways in which we could fix the problems. The whole day made me very hopeful about the prospects for significant progress in the tools and techniques for TDD and refactoring.
Updated 2010/02/06: Ben Stopford has written up his perspective on the workshop and uploaded his PDF slides.