Making assumptions based on incomplete information

Making assumptions and forming conclusions based on those assumptions can lead to wasted time and effort on the part of your project team. Anytime you are ready to form a conclusion about a cause and effect, ask yourself the question, do I have all of the information that I need to be 100% sure that this is the correct conclusion. If the answer is no, then ask yourself, how sure am I percentage-wise, 50 - 60%, 70 - 80%, 90 - 95%. If you are about 90% sure, that may not be enough. Ask yourself, what will it take to be as close to 100% sure as I can possibly be? Is there someone that I need to contact? Is there another test that I need to run? Very often there is another test that you can run but the effort to set it up may not be worth additional information gained. You need to think about the relative cost versus benefit and make a decision based on testing intuition. Below is a story about an assumption I made and how it caused extra time and effort to get my TV remote control to work.

One Sunday afternoon my wife and I were watching a movie. She got up to go to the kitchen. I pressed pause on the DVD remote and decided to switch to the TV to see the score of a basketball game. I hit the "Input" button on the TV remote but the DVD was still showing on the screen. I hit the button again and it still didn't switch to the regular TV. I then tried hitting other buttons on the remote, attempted to adjust the volume, change the channels and still no response. I tried all of the other buttons and none of them worked. I decided (without complete information) that the remote was the source of the problem. So I took the batteries out and put them back in and then tried the remote, that didn't work. I switched the batteries and tried again, this time the volume adjusted but the rest of the buttons didn't work. I decided it must be the batteries so I got up (notice my goal was not to get up) and went to the kitchen, found some new batteries, and tried the remote again. The remote still didn't work. Now I determined it wasn't the remote at all so I investigated the TV and discovered that my daughter’s toy was covering the TV infrared sensor. I felt pretty silly because I had a funny feeling it wasn't the remote but all of the information that I gathered led me to the conclusion that it was - new information led me to the correct conclusion.

How many of us have been burned by this tendency to assume without complete information. How many times have we wasted our time, or worst - someone else's time chasing solutions to problems that really didn't exist? My feeling is that software testing is an adventure that is made easier by playing close attention to details and our tendencies to buy into false assumptions. By having a mindset of skepticism about the assumptions behind cause and effect of application behavior, we can reduce time spent doing non-value added tasks and increase our test effectiveness exponentially.