Tester surprises everyone

"Oh this is also the functionality, I didn't know", have you ever heard this line from developers, probably yes. Many times we find a scenario which even developers are not aware of. This happens because each developer works on his/her module and may not be aware of the big picture of the product. Many times even product owner gets surprised with the issues which testers find in testing, because even he/she might not have thought from that point.

Product owner usually defines high level requirements so, it is the responsibility of the requirement gathering team to ask correct questions to get details. Many requirements are very obvious for PO since he/she is very familiar with the product domain, but those small and obvious requirements might play very important role in development and testing of the product.

PO looks at the product from user's point of view and a developer looks at the product from technical point of view. But a tester actually looks at the product from both user's point of view as well as technical point of view, so it is very important for him to be part of requirement gathering. Moreover everyone (developer / TL / PM / PO) look at the tester as a domain expert. So it is very important for tester to get some domain knowledge before actually starting testing. He has to think out of the box to find out some very important and severe issues in the product.