Once upon a time, a long, long time ago, well some 20 years actually, some clever folk figured out a way of structuring work that was quite revolutionary. So revolutionary in fact that most people didn’t understand it. Now a few folk in a parallel world worked hard over the years to make this method work, and they invented more ideas, frameworks and tools. And every day they are constantly improving their productivity and quality; and many of them also use Agile methods, as they are entirely complementary to the revolutionary method. The method – Design by Contract.
However the mainstream of the market seems to be fixated on Agile methods, as being the metaphorical silver bullet. Yet we all can’t help noticing that Agile Land is not such a happy place. There is continuing debate about the difficulties of making the methods work in the enterprise; the fragmentation of the original Agile principles and the outbreak of religious wars. And I am minded to comment, again, that the root problem with Agile methods is that they are one-dimensional – solely focused on people and process to the exclusion of all the other opportunities to create agile businesses.
At the heart of the conundrum is the need to focus on some different questions. Such as:
– How can we reduce the amount of work that has to be done?
– How can we structure the outcomes (deliverables) so they are inherently agile?
– How can we structure the work so that there is real traceability between the intrinsic business model and the delivered systems and services?
– How can we ensure that overall technical debt is always reducing faster than new functionality is being delivered?
– . . .
You get the idea.
So back to my parallel world. In Design by Contract the business problem, typically the Use Case, Services and Operations are attributed with Pre-conditions, Post-conditions and Invariants (rules that must remain constant). These artifacts provide us with functional and design level specifications that can be produced in an Agile, iterative manner, that
a) Deliver implementation independent service specifications (descriptions if you prefer)
b) And therefore also for publishing API specifications
c) Form the basis for structuring the code that is fully traceable to the business model
d) Create inherently agile systems and service structures
e) Create the structure (stubs) for Unit, Integration, Functional and Regression testing
(e.g all conditions and rules within a given test scope must be tested)
f) Depending on the technology employed to define the conditions and invariants, (rules engines, pseudo languages etc) both code and test cases can be produced automatically.
I was prompted to write this blog because I happened to read Rob Marvin’s useful blog on testing, and his very interesting ideas for improving test productivity to keep up with Agile projects. In his piece he talks about automation, but actually seems to miss the opportunity to auto-generate the test cases. Even more important, he seems to believe that the current state of Agile projects is his benchmark that he has to keep up with. I would comment that state of the art Design by Contract projects together with model driven frameworks are delivering order of magnitude greater productivity with exceptional quality, and this ought to be the where testers should set the bar.
Sometimes it seems to me that the Agile methods community is rather in the situation of hoping a Fairy Godmother will appear, wave a magic wand and all will be well. Everyone will use Scrum like they ought to; enterprises will waive their awkward little requirements for inter-project coordination and all will be well. But while the Agile community continue to ignore the broader scope of agile enablers this day won’t come.
If you are interested in an example of Design by Contract at work take a look at the Agile Service Factory.
