Whether or not you should confess when you like a friend of the opposite sex who has a good relationship with you depends on how much you like him, I think. Of course, I do not recommend direct confession, but need to test first. Since you like a close friend of the opposite sex, you must have some knowledge about the other person. So, when you realize that you like him, you can try to find out if he likes you as well. For example, you can find an opportunity to chat, try to pull to the issue of male and female friends, and then ask each other like what kind of other half, or ask as if there is XX like TA, ask TA whether you are willing to by you to set up the two of them together, note that, try to explore the time to be sure to observe each other's reaction.
Or if your relationship is so good that you can joke about anything, you can start by cracking a few jokes, and then continue to joke around at the right time, saying, "You're so good that I want to chase you," and so on, and then observing her reaction after that. I think, since your relationship is relatively good, see the reaction should be able to roughly see each other to you in the end there is no meaning. If you feel that the other person is not averse to the topic of boyfriend/girlfriend, then, you can confess. But in order to be able to continue to be friends in the future, so, the confession of the time also need to pay attention to the wording, do not make the atmosphere too awkward, and do not force the other party to give you an answer right away, you can give the other party to stay in time to think about. If you are still worried, you can also explain to each other do not need to have too much psychological pressure, if you can not accept the words, I hope the future is still friends and so on. Finally, if you really do not have any certainty, I think it is better not to rush to confession, you can first slowly cultivate feelings.