Software testing pervades the entire software development process. This part of the book focuses on three phases of testing: unit testing, regression testing, and integration testing. A significant challenge in regression testing is the selection of tests to rerun. Methods for the selection of a subset of tests to rerun are covered in Chapter 9. Unit testing is covered in Chapter 10. Unit testing is used widely in the industry. Here the focus is on tools for unit testing and some techniques, e.g., the use of mock objects, that make unit testing easier.

Deciding a suitable sequence in which components of a system are to be integrated is the test order problem. There exist several solutions to this problem. Some of these are discussed in Chapter 11. This chapter also introduces a variety of terminology that is often used in integration testing.

Tasks performed in other phases of testing including unit testing and system testing are covered across several chapters. These tasks include test generation and adequacy assessment. Tools useful in these phases are also sampled in other chapters.