During the CAST 2014 conference in New York I participated in a workshop by Laurent Bossavit and Michael Bolton called “Thinking critically about numbers – Defense against the dark arts”. Inspired by this workshop I took a look at one of the Dutch sites addressing news about software testing www. testnieuws.nl. This is the second post to come out my curiosity.
On May 23, 2014 Testnieuws hosted an article “Code inspectie is 80 procent sneller dan testen” (translated Code inspection is 80 percent faster than testing). The article itself provides little more substantiation for the claim than a reference to research by IfSQ. Both the claim and usage of this as header seems to only serve to grab the readers attention. The article ends with an invitation to read more about it and this leads to what I think is the actual article “Status ICT-projecten vaak compleet onduidelijk” (translated “Status of ICT projects often completely unclear). This article describes that, especially government, projects need to have more objective information and they need to get it earlier. This way it is possible to determine the status of a project. Andres Ramirez, Managing Partner of the OSQR Group states that “better software leads to better projects” and “better source code leads to better software” and “the quality of source code can be objectively assessed by the guidelines from the Institute for Software Quality”. The last quote explains the IfSQ abbreviation used earlier.
A little further in the article the claim is used and even extended “Code inspection is 80 percent faster than testing, and finding and repairing code is much cheaper than testing”. Ramirez also adds “Research by IfSQ shows that regular code inspection during the production process ensures that software can be changed more easily. Inspected software is 90 percent cheaper to maintain.”. I am choosing to ignore these last claims for now and proceed to IfSQ the look into their research.
The IfSQ – Research Findings Relevant to the IfSQ Standards hosts about 50 or so reference to articles and research results divided into sections “Why should you inspect software?”, “When should you inspect software?” and “What should you look for?”. Noticeably the focus is strongly on code quality and, to my opinion, therefore not really on software quality as such. Also there seems to be need to position code inspection opposite to testing as suggested by titles like:
- “Code inspection is up to 20 times more efficient than testing“
- “Code reading detected about 80% more faults per hour than testing“
The second title points to a page with the title “Inspection is 80% faster than testing” which indicates I am on the right track. The page however only repeats “Code reading detected about 80% more faults per hour than testing.” and provides two, non IfSQ, sources for it without further argumentation. The sources are:
- Comparing The Effectiveness of Software Testing StrategiesRecorded 1987 in IEEE Transactions on Software Engineering, SE-13, no. 12, December;
Pages 1278-96 by Victor R. Basili, and Richard W. Selby
- Software Inspections: An Effective Verification Process
Recorded 1989 in IEEE Software, 6, no. 3, May;
Pages 31-36 by A. Frank Ackerman, Lynne S. Buchwald, and Frank H. Lewski
So, at least in this case, so called research findings by IfSQ do not point to research executed by IfSQ themselves, nor were they involved as both sources are quite old and IfSQ was established much later in 2005. Next step to identify which of the two sources holds the quote.
The first article was easily found. In summary the article describes a scientific study that applies an experimentation methodology to compare three (then) state-of-the-practice testing techniques: a) code reading by stepwise abstraction b) functional testing using equivalence partitioning and boundary value analysis, and c) structural testing using 100 percent statement coverage. It compares three aspects of software testing: fault detection effectiveness, fault detection costs and classes of faults detected. It focussed on unit testing code using a limited set of specific programs, known errors and a mix of academics and professional developers.
Although it found difference between the three test techniques with in some instances an identifiable hierarchy of code reading, functional testing and structural testing non of the results came anywhere near the claim of being 80% faster. So my conclusion is that this article cannot be a valid source for this claim.
I could only find the second at IEEE and as a result the article could only be read by buying it. Setting aside my initial dislike of paying for information, especially if it so old, I tried to buy it. Unfortunately the cash module did not like my dutch creditcard. As a result I stuck to a number (4) abstracts and a course summary of where the article was used.
The second article came closer to the IfSQ description of code inspection in describing how its done, what is needed for it and what it can measure. Still none of the abstracts said anything about being faster than testing. They did mention percentages around 80% for defects found by software inspections. This to me is a different claim. Sounds to me that a ‘leaky’ inference was made and worse another attempt to gain credibility by bringing testing in disrepute.