Life should NOT be a trip to the grave with the intention of arriving safely in an cool and well preserved body, but rather to skid in, chocolate in one hand, beer in the other, body wrecked, totally worn out and screaming WOO HOO what a ride!
We normally estimate 20% for testing in our project, and we normally find it is only enought to perform testing. I asked this question in my QC class I recently joined, and the teacher said that it's normally 40% (for all elements in test cycle: time to understand requirement, produce test plan, write test cases, execute test, report resutls, and analyze the test results).
But it is your negotiation skill to achive this level [img]/images/graemlins/smile.gif[/img]
I think you will get the estimated time for your testing project from your previous and similar projects in your company (i.e. Historical data). Or you can use COCOMO model to get the estimated time for the testing phase. Am I correct?
There is another simple way that is (sadly) often used in software projects to compute the time for the testing phase: it just take the time remaining after coding is finished and before the scheduled delivery deadline of the project. Example: for a 6 (elapsed) months project, if programming finish after 5 months, then testing takes only 1 month, so around 17% of the project ;o)