You can only predict things after they occur

“You can only predict things after they occur” This quote was attributed to Eugene Ionescu in the source I had.

There are several related quotes:

“Those who have knowledge don’t predict” and its corollary “Those who predict, don’t have knowledge.”

Or lastly: “The best way to predict the future is to create it” (Peter Drucker).

Maybe we could use these quotes the next time someone says how long testing is going to take.  The interesting part is when you push back and say: “How long did it take last time?” or “How much bigger (in whatever the favourite measure is) is this project compared to the last one?”.  Neither of those questions elicit much useful information or a response at all so the analogous method using internal numbers is unavailable.

If you have no previous statistics from the organisation, there are lots of statistics available online or you can use one of the Estimation Methodologies (PERT, Planning Poker, WBS, Function Point Analysis or Test Point Analysis).  They provide a good starting point but must be adjusted for the particular situation. 

One of the major aspects of Quality Assurance is to gather up statistics on what occurred last time and use that to predict the future. While no one can get 100% accuracy, it certainly helps to know what occurred in the past.  Adjust for the situation at hand and go forward.

Software Testing solves problems for yesterday and today.

Quality Assurance solves your problems coming tomorrow!