Sharing an answer to a couple of recent customer queries in hopes that it is generally useful as well:
Often in discussing the value of estimating test efforts, a comment is made by someone that there is no point in doing so as they will be given only 2 weeks (or some other arbitrary number) for testing anyway.
In such a tightly constrained situation, it will frequently feel that there is no ability for the test team to control or even influence the situation – it is clear to everyone on the team that there is not enough time to do the job, but that is all the time there is, and so…
It is the next thought after that which is critical: so… what do you do? What is your plan or strategy of testing? And how do you know that this approach is the most effective compared to another? How do you make it visible to the stakeholders and senior management what they will get for the 2 weeks (and what they won’t get)?
This is where estimation can help by allowing the rapid generation and comparison of different efforts, by allowing the effort required for a given test approach to be quantified, by translating a schedule constraint of working days into a budget of person days and vice versa, by revealing opportunities to get testing involved earlier in the SDLC where they won’t be on the critical path, etc.
Just because you are tightly constrained does not mean that you can not take control and ownership of the problem, think it through, come up with the best solution approach possible for the situation, and succeed together as a team.