It also helps me understand why it is so hard to estimate how long it will take to test something.

I like how you’ve used numbers(!) to explain what not to do with numbers, it’s a clever way to deal with people who focus on numbers too much.

I would like to add few more things why testing takes so long. As you say: "All models are wrong. Some are useful". Any plan is a model, thus it doesn't cover every possible combination and thus it is wrong. Especially big problem is it for managers, who consider plans more-less accurate. This usually comes from their ability to do budgeting. In budgeting plan you can't vary so much and thus they tend to expect all other plans to work the same way. However in testing which envolves much more unknowns (I think that it mostly consits of unknowns) these plans fail for that reason. If you have big unknown then you can't plan based on it. It is like when I throw handful on needles into haystack of unknown size, give you limited time, won't tell you how many I through in and tell you to find all of them with that time. You start looking but whenever you find one you don't know if this is the last one. If you don't know the size of haystack and amount of needles you can't quess how long it might take to find them all.

Another things that tends to affect time used for testing. As new development goes on and new features are added the amount of testing needed to be done increases exponentially. If we have to test how many ways are to place numbers 1,2,3,4 in sequence then there would be 24 possibilities. If we add 5, then there would be 120 possibilites. thus increasing total size of , the amount of testing would increase 500%. Of course this is again just a model with very big simplifications.

Will be waiting for your next posting
Oliver Vilson

I don't know which team I belong to as I can see myself working with all the three teams.

But I really appreciated your efforts for such a simple explanation for us!

Best Regards,

Amit

testing is my passion!!!
http://bugteaser.blogspot.com/