Test driven development book

• Test Driven Development By Example
• Refactoring: Improving the Design of Existing Code
• Extreme Programming: Embrace The Change

Growing Object-Oriented Software, Guided by Tests by Addison-Wesley - it is about mocking frameworks - JMock and Hamcrest in particular.

From description of the book:

Steve Freeman and Nat Pryce describe the processes they use, the design principles they strive to achieve, and some of the tools that help them get the job done. Through an extended worked example, you’ll learn how TDD works at multiple levels, using tests to drive the features and the object-oriented structure of the code, and using Mock Objects to discover and then describe relationships between objects. Along the way, the book systematically addresses challenges that development teams encounter with TDD--from integrating TDD into your processes to testing your most difficult features.

EDIT: I'm now reading Working Effectively with Legacy Code by Michael Feathers which is pretty good. From the description of the book:

• Understanding the mechanics of software change: adding features,
  fixing bugs, improving design, optimizing performance
• Getting legacy code into a test harness
• Writing tests that protect you against introducing new problems
• This book also includes a catalog of twenty-four dependency-breaking techniques that help you work with program elements in isolation and make safer changes.

I read it already, it is one of the best programming books I've ever read (I personally think that it must be called Refactoring to Testability - it describes the processes for making your code testable). Because a testable code is good code.