TL;DR
Learning to say “No” is an essential part of becoming a passionate software tester. We can choose to say no in several situations. The post is based on a remarkable book written by Chad Fowler, The Passionate Programmer.
At CAST 2016, I attended half-day training: Fiona Charles: Learning to Say No. That was the first time I considered that is ok in daily work in some situations to say no. Up to that time, I was an always Yes person. So, when is ok to say no?
You Can Not Commit To The Yes
There are situations when you are 100% sure that you can not commit to the yes. In that situation, you need to provide reasonable facts about why you can not to do the commitment.
You Do Not Know How To Do It
You do not have the knowledge to commit for that Yes.
Volunteer Work
Aka. work not paid with money. Here you need to negotiate. The side that asks you for “free” work can offer other benefits. Or doing actual work has some advantages. If there is nothing there for you, try to negotiate none money benefits. It this fails, you are free to say No.
The King Is Naked
At meeting, somebody above your rank states that we have to do it in that way. If you have reasonable facts that this will fail, feel free to say No.