One never wants to be the teacher who has the "gotcha" attitude--the one who creates an environment waiting for a child to fail. You don't want to be an antagonizer who tests students and makes life difficult for them. I have to say this is an attitude I rarely to never see in schools--almost every teacher I work with tries to create situations that invite students' best effort and success.
Sometimes, however, there will be situations where someone is just waiting for a learner to fall. They sit in the stands watching keenly looking for error. This kind of attitude makes everyone uncomfortable.
Instead I much prefer direct, straight talk about issues and error--the kind of talk that deals explicitly with what's happening and what could change for the better. I don't believe in "gotcha," but instead "let me help you--what can I do to make things work well for you."