Professional C__ - Marc Gregoire [441]
Chapter 26
Becoming Adept at Testing
WHAT’S IN THIS CHAPTER?
What software quality control is and how to track bugs
What unit testing means and how to use it in practice
What integration, system and regression testing means
A programmer has overcome a major hurdle in her career when she realizes that testing is a part of the software development process. Bugs are not an occasional occurrence. They are found in every project of significant size. A good quality-assurance (QA) team is invaluable, but the full burden of testing cannot be placed on QA alone. Your responsibility as a programmer is to write code that works and tests to prove its correctness.
A distinction is often made between white box testing, in which the tester is aware of the inner workings of the program, and black box testing, which tests the program’s functionality without concern for its implementation. Both forms of testing are important to professional-quality projects. Black box testing is the most fundamental approach because it typically models the behavior of a user. For example, a black box test can examine interface components like buttons. If the tester clicks the button and nothing happens, there is obviously a bug in the program.
Black box testing cannot cover everything. Modern programs are too large to employ a simulation of clicking every button, providing every kind of input, and performing all combinations of commands. White box testing is necessary because it is easier to ensure test coverage when tests are written at the object or subsystem level. White box tests are often easier to write and automate than black box tests. This chapter focuses on topics that would generally be considered white box testing techniques because the programmer can use these techniques during development.
This chapter begins with a high-level discussion of quality control, including some approaches to viewing and tracking bugs. A section on unit testing, one of the simplest and most useful types of testing, follows this introduction. You will read about the theory and practice of unit testing, as well as several examples of unit tests in action. Next, higher-level tests are covered, including integration tests, system tests, and regression tests. Finally, this chapter ends with a list of tips for successful testing.
QUALITY CONTROL
Large programming projects are rarely finished when a feature-complete goal is reached. There are always bugs to find and fix, both during and after the main development phase. Understanding the shared responsibility of quality control and the life cycle of a bug is essential to performing well in a group.
Whose Responsibility Is Testing?
Software development organizations have different approaches to testing. In a small startup, there may not be a group of people whose full-time job is testing the product. Testing may be the responsibility of the individual developers, or all the employees of the company may be asked to lend a hand and try to break the product before its release. In larger organizations, a full-time quality assurance staff probably qualifies a release by testing it according to a set of criteria. Nonetheless, some aspects of testing may still be the responsibility of the developers. Even in organizations where the developers have no role in formal testing, you still need to be aware of what your responsibilities are in the larger process of quality assurance.
The Life Cycle of a Bug
All good engineering groups recognize that bugs will occur in software both before and after its release. There are many different ways to deal with these problems. Figure 26-1 shows a formal bug process, expressed as a flow chart. In this particular process, a bug is always filed by a member of the QA team. The bug reporting