TestBash Home 2020 — Explore Black Box Puzzle #35

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Black Box is a scary word for many software testers. I was, for sure, one of them. The first thought when I hear word black box was I do not have a clue what is going in here! I considered that as bad thing. How can you use something when you do not know how to use it? Years later, I realized that this is a fun part of software testing, going from chaos to obvious. Repeat again on the new black box.

James Lindsay is the author of Black Box puzzles. In the first five minutes of the session, he asked to feedback about our progress. One tester admitted that she is confused. And that is good, James (master) added.

The Puzzle

Here is my take on the puzzle. There is an interesting thread on Software Testing Club from other participants.

The Session

Putting lights in a queue. Queue fills from right to left.
Queue timer starts when light is turned on. And that counts for next light added to row queue.
Each row has independent timers.


This means that second row light will not go off after four seconds of its appearance time moment, but four seconds after the moment when the first light went on.

Queue timer is started when the first light goes on. But that rule is applied only for the last light in the queue (top of the queue). When the last queue light goes off (first on the right in a row), the next light will go off when the full-timer value expires.

I used my phone stopwatch.

I measured how much time elapses before the light goes off. I could not get consistent times for the last light in the queue.

For exercise.

  • with the right button.
  • with the left button.
  • alternate left and right buttons.
  • alternate right and left buttons.

Measure timings.

Originally published at https://blog.tentamen.eu on May 8, 2020.

Written by

Founder of Tentamen, software testing agency.

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