Listen to this wonderful presentation by Kent Beck on Developer Testing.
Kent Beck is widely recognized as the father of eXtreme Programming and JUnit. Kent's other contributions to software development include patterns for software, and the rediscovery of test-first programming.
He is the author/co-author of Extreme Programming Explained: Embrace Change 2nd Edition, Contributing to Eclipse, Test-Driven Development: By Example, Planning Extreme Programming, The Smalltalk Best Practice Patterns, and the JUnit Pocket Guide. He received his B.S. and M.S. in Computer Science from the University of Oregon. Source : Kent Beck on Developer Testing.