Guess the Number

Th11     Start Time : 14:15     End Time : 16:00

Talk Abstract:

In this workshop we will do an exercise called Guess The Number.
It is a simple, but difficult exercise consisting of a Windows executable with a command-line interface, so many of you must bring computers. We will split up in groups, because it is even more difficult on your own. It stimulates logical thinking, critical thinking, and creativity.

Most of you probably won’t solve the exercise in an hour, but we will break at that time so we can do a proper debrief. You will not get actual hints, but might get inspiration about how to think. Some of you will be frustrated, or even upset, but that is not dangerous. It can be solved in 10 minutes; if that happens, we will pat your back and you can watch the others struggle.

During my years as teacher at higher vocational studies I co-created more than a hundred exercises on various topics. This one was one of the first tries with a custom-built hands-on application. It was pure luck, but the simplicity of the puzzle turned out to be very intriguing. Combined with the experienced learning it gives, it is a one-hit-wonder that demands a wider audience.

Myself and co-creator Henrik Emilsson have done the exercise dozens of times, and it can be more fun to watch the “victims” than to do the exercise! (I showed this exercise at EuroSTAR 2015, so if you know the solution you are allowed as spectator.)

Attendants will be given the executable and instructions to take back home, and are allowed to do the exercise with their friends, but not to publish it or spread to a wider audience.

Key Takeaways:

  1. Get experienced learning of key aspects of testing
  2. It is fun and good to work together
  3. You can bring the exercise back home

Back to Programme

  • Speaker

  • Rikard Edgren - Test Expert, Nordic Medtest, Sweden

    Rikard Edgren describes himself as a humanistic and technical tester since 1998, specialized in generalities like test strategy and exploratory testing. Thus far Rikard has had eight speaking appearances at EuroSTAR and was a winner of the Best Conference Tutorial Award in 2014, and Programme Chair in 2018. Rikard is a member of the think-tank The Test Eye, co-author of Software Quality Characteristics, author of The Little Black Book on Test Design and Den Lilla Svarta om Teststrategi and a contributor the EuroSTAR’s recent publication ‘The Little Book of Testing Wisdom‘.
    Rikard currently works as Test expert at Nordic Medtest, Karlstad, Sweden, working with Swedish healthcare infrastructure.

  • Co-Speaker

    Henrik Emilsson - Nordic Medtest Sweden

    Henrik Emilsson have a long and broad experience in the software testing field and currently holds the position as Test Strategist at Nordic Medtest in Sweden. He is one of the founders of the think tank The Test Eye (; co-founder of the Swedish test conference Let’s Test; and have arranged two SWET-meetings (Swedish Workshop on Exploratory Testing). He has been a speaker at EuroSTAR (2005, 2012, 2016), CAST (2011), and several other conferences. Henrik has created a two-year course in software testing (college of higher vocational studies) where he also was a teacher. He has also been teaching on several other courses, including in Software Test Design at Karlstad University. Other engagements worth mentioning is his two-time appearances in the EuroSTAR TestLab, and co-founder of the local chapters of SAST (Swedish Association for Software Testing) in Gothenburg and Karlstad.