I'll start with a true/false test. It's a bit rigged, but I think you'll see the point.
1. Testing is good for your IFComp entry. T/F
2. Testers can find bugs you can't. T/F
3. Testers can suggest features you didn't see that will make things easier. T/F
4. Testers will try the stuff you maybe didn't have time to, which saves you time and the necessity of backtracking when you really want to focus on one feature. T/F
5. Testers remind you of stuff you forgot to implement. T/F
6. It can be hard to ask testers for their time, but people are generally nice and willing. And even a 20% response rate is very good. T/F
7. It's worth working through the emotional crush of seeing where testers got stuck, because it motivates you to look for other things. T/F
8. Different styles (go fast/go slow, supercritical/super encouraging, knows the programming language/doesn't) of testers turn up different things. Whatever you're writing is hopefully far more interesting than a standardized test, so even a lack of skill can be a huge help. T/F
9. Starting testing earlier is better, because then bugs that were hidden and hard to find are more likely to turn up, and issues you just can't deal with right away may become clearer in a month. T/F
10. You should have minimal programming-tests you run before sending something to testers, so that their time is used the best they can. T/F
I bet you got 10/10 and would've even if the answers weren't all true. I could go on like this for a bit. But ever question I write out, I've violated in some way.