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Testing: the Discipline of Detecting Defects

​The second edition of Anne Mette Hass’ book Guide to Advanced Software Testing is now available. Since the book first appeared in 2008, the ISO 29119 Standard for Software Testing has been released. The new edition includes a bridge from the International Software Testing Qualifications Board (ISTQB) certification to the ISO standard. In this article, Anne Mette Hass introduces the book and shares some of her thoughts on testing.

The book, Guide to Advanced Software Testing, was originally a textbook written for students taking the ISTQB exam, which is an international certification in software testing.

“I worked as a certified teacher, and I wrote the book to assist my students as, at that time, there wasn’t any comprehensive text­ book available which covered the ISTQB syllabi, i.e., the foundation certification and the advanced certifications for test managers, test analysts, and technical test analysts. What started as notes became an educational book on testing,” says Anne Mette Hass.

Since the book first appeared in 2008, a new standard for software testing has been released: ISO 29119 Standard for Software Testing. Apart from introducing the ISO standard, the book provides a comparison between the ISO 29119 standard and the ISTQB syllabi and how to bridge them.

With the second edition, readers are furnished with a systematic approach covering areas such as Test Management, Test Case Design, Test Techniques and Test Tools and Automation, but also with softer topics, such as People Skills.

This book is for people wanting to take an ISTQB certification, especially at the ad­ vanced levels. However, according to Anne Mette, it is also the kind of book that any tester would put on the work book shelf and consume chapter by chapter or use as a reference work.

“With this book, I hope I can inspire people to develop their skills so that they can become even better testers.”

ISO 29119 Software Testing Standard

Anne Mette Hass has been part of the inter­ national working group which, over a period of several years, has been collaborating on establishing the ISO standard, covering all of the test processes, test related documents, and test case design techniques.

The first three parts of the ISO 29119 standard came out in 2013. ISTQB has stated that their syllabi will be changed in order to comply with the ISO standard over time.

The tester’s mindset

“As a tester, you want to provide as much information as possible about the quality of the software. In doing so, you should be look­ ing for the defects in relation to expectations. Expectations, however, often provide an incomplete picture, and then, as a tester, you will have to ask what the full expectations are. It is not enough to know ‘if a, then b’; you need to know what the system should do ‘if not a.’ Otherwise, you risk launching systems with potentially failure­prone software.

This was literally the case with the rocket, Ariane 5. The rocket suffered the dismal fate of self­destruction only 40 seconds after launch due to a software bug. Basically, a software component from the previous rock­ et, Ariane 4, was reused in a backup system, and as this software interacted with the new software, it led to an overflow error causing a cascade of events leading to the explosion. Fortunately, Ariane 5 was unmanned. Nevertheless, it was an expensive loss and a bitter day for European space research.

“The example serves to show that although you have a piece of software that you, by experience, know is working, you can’t assume that it will work the same way when you change the conditions. Some of the inter­dependencies are so subtle and intricate that even minor changes can have a huge impact.”

“What’s more, it doesn’t have to be a rocket to be mission critical. Today, there is software in all kinds of systems, and to our customers, it is mission critical that the production systems are running and that major failures are avoided,” Anne Mette concludes.

The golden rule of testing

Today’s systems are very complex. There are almost an infinite number of things you can test in so many combinations. They could all be all right, but experience shows some of them, most likely, are not. You can never exhaust the testing possibilities. The question is: ‘When are you done testing?’

“There is a ‘golden rule of testing’: when you have to stop, you should have done the best testing possible. You can’t exhaust all the possibilities for testing. That’s why we operate with risk­based testing. You base your test on a risk assessment of the product: where will it do severe harm if there were a defect, what are the odds, and what does your experience tell you? Then, you revisit the risk analysis – was there something you overlooked? Everyone makes mistakes; human error is a fact for everyone involved in software devel­ opment. And it can be fatal to disregard this. That is why we test. Testing is the discipline of detecting defects.”

Read more books!

“If I were to give a piece of advice to testers, I would encourage them to read books; not just my book, but books on software develop­ ment in general, as well as programming and testing. I encourage people to read, because traditionally there is a hands­on­approach to testing as a discipline, rather than an aca­ demic one. Hands­on is great, but in my opinion it doesn’t hurt to have a theoretical basis as a supplement to your experience. I wish it were possible to get a university degree in testing. It would professionalize the discipline immensely, but while we are waiting for that, the new ISO standard is a great leap forward.”


Get the book here
The book is published by Artech House and can be ordered by sending an e­mail to artech­ Anne Mette Hass can be booked for on­site training sessions and presentations. Please contact Anne Mette Hass on for additional information.







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