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Test Process Improvement Model - test techniques v subject matter knowledgeThe TPI model would have us believe that an understanding of test techniques is more important and valuable than subject matter knowledge. Is this true? Well, yes it is, but only if a structured approach is followed in system analysis and design. I think that one of the most valuable concepts I have come across in the field of software testing is the concept of equivalence classes. That is, of course, that if certain classes of data are equivalent then we can justify one test case per class, thus drastically reducing the number of test cases. If only more consideration was given to this during the design stage of the systems we test. Because of the piecemeal fashion in the way that a lot of systems are designed we end up with a huge amount of unnecessary functional complexity. Hence the importance to the businesss of subject matter expertise in not only the execution of tests, but also data preparation. That's why we have a huge number of testers with a reasonable knowledge of test techniques who can't necessarily put their expertise to best use.
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Subject matter knowledge v test techniques: another view
It's an interesting consideration: is 'testing' knowledge more or less important than 'subject matter knowledge'. You know what I'm going to say.... "it depends" :-) and I'm sure you appreciate the influences that might shift the balance. Perfect requirements versus missing requirements is an obvious one.
This debate quickly shifts towards a different question. "Are business people with testing skills more effective than testers with generic testing skills?"
But rather than get into that debate, it strikes me that we should look at the cost of acquisition of these skills or knowledge.
In the Competency-Based Tester Certification debate in the Forum yesterday, there did seem to be general acceptance that existing schemes provide a relatively small component of a tester's competency. The skills of test design techniques must therefore be a smaller sub-component of this.
The underlying assumption must therefore be that it takes a relatively short time to learn the technqiues. A day or two to learn the top four or five black-box techniques. (Of course one can expand this by teaching more generalised BB techniques and subjecting candidates to larger and complex requirements to test).
But how long does it take to acquire the subject-matter expertise to understand imperfect requirements? How long does it take to build up one's network of peers who one can consult on such matters? It could take years of course.
I'd say the value of test techniques and subject matter expertise is comparable. The cost of acquisition of those skills is another matter.
I'm pretty certain that in most contexts, it's faster and cheaper to train business people to become testers than train testers in the business.
Susan and I set up Aqastra to provide training of business people in critical thinking, testing theory and practice and tester-specific technology skills on this important foundation.
And on TPI? Well it takes the position you say because essentially, it is a method for implementing T-Map. So the TPI position is a self-fulfilling prophecy.
subject matter knowledge v test techniques
Interesting! If people behaved rationally then the business people would be more interested in acquiring "general" testing skills than the testers would be acquiring "specific" business knowledge. ( see my blog on Becker's ideas about "specific" and "general" training ) Because "general" skills are transferable and can be used elsewhere whereas "specific" skills are not and can become redundant. So that strengthens your argument!