No developer like bugs. It means extra hours of work for him. But it is much better for a developer to get a bug from a tester than an end user. So developers should encourage testers to find more bugs.The psychology of developer is to create a system that does not break and the psychology of a tester is to break that system.

To find defects in a system a tester needs

1. Curiosity

2. Attention to detail

3. Professional optimism

4. Critical Eye

5. Good Communication skills.