I was demonstrating this on a projector which only supported a resolution of 800x600. So if I wanted to keep the windows calendar and webpage always visible, my webpage real-estate becomes considerably reduced. To the surprise of my audience I started resizing the browser window so that I can see more of the region surrounding the widget, which seemed unnecessary since the widget only took a small portion of the entire webpage. I explained that I want to be aware of problems surrounding the widget while I am executing my tests on the widget. I did confess that I do not know what kind of problems could appear in those regions but it doesn't hurt to pay attention.
This was a demonstration of exploratory testing. I was narrating my choices of executing certain tests that I generated on the fly, and why I chose to ignore other tests that I considered as equivalent or not related to my current test objective. A few minutes into the testing, one of my colleagues discovered that a button's outline at the corner of the web page was blinking as I was invoking the widget. The audience appreciated this discovery since they could relate to my initial preemption. I myself did not notice this due to inattentional blindness.
Before we continue, I think a good way to explain inattentional blindness is with the example of a magician's performance. Ever notice how a magician sometimes tries to distract you away from his actual trickery by trying to focus your attention on something else. For example, when a coin that you can swear was in the palm of the magician's hand disappears into thin air when he unfolds his fist. In reality, the coin was swiftly removed while you were paying attention to where the illusionist wanted and hence the perception of magic. This is called inattentional blindness. You can't see what is right in front of you, simply because you were paying attention to something else.
The irony of my episode was that I did not discover the problem even though my intention was to pay attention to such peculiarities. Also, exploratory testing is supposed to be better at minimizing inattentional blindness. This symptom is advocated as being more common during scripted testing. So I tried to analyze this phenomenon and came to the following explanation.
Since I was sitting close to a large projection of the screen on the wall, my visual field was limited. This made me more prone to inattentional blindness. Also I was frequently alternating my attention:
- To find important problems in the widget.
- To explain to the audience the reasons for my actions.
- To make sure my explanations were comprehensible.
- To address queries from the audience.