First and foremost our job is to find issues fast. The sooner we find a possible problem, the sooner it can be identified as a real problem and eventually solved. To find these issues and to identify them we need to work with the team. A tester, or a team of testers cannot function to its full maximum potential alone.
We find these issues by ways of learning. Learning about the product, project, team, oracles,…
The things we learn enable us to inform the stakeholders with a unique point of view.
Keeping in mind that testing activities are by nature infinite we need to focus on testing as much as possible during the given time frame, trying to attain as much useful coverage as possible. It is also our responsibility to focus the testing effort to where we expect there to be important errors.
In short, we look at the work pragmatically and estimate what should enjoy most of our effort.
When met with dubious project decisions and possible implications to quality these risks should be reported clearly and supported with evidence. Often, these reports are not met with much rejoicing. However, saying out loud what nobody wants to hear, but has to hear, is part of our mission too.