Introduction to Software Testing

One of the most widespread changes in software testing during the last decade has been the increased use of test automation. We introduced test automation in Chapter 2 as implementing tests into executable test scripts. This chapter expands on that concept, starting with a complete definition.

Software testing can be expensive and labor intensive, so an important goal of software testing is to automate as much as possible. Test automation not only reduces the cost of testing, it also reduces human error and makes regression testing easier by allowing a test to be run repeatedly with the push of a button.

Software engineers sometimes distinguish revenue tasks, which contribute directly to the solution of a problem, from excise tasks, which do not. For example, compiling a Java class is a classic excise task because, although necessary for the class to be executable, compilation contributes nothing to the behavior of that class. In contrast, determining which methods are appropriate to define a data abstraction in a Java class is a revenue task. Excise tasks are candidates for automation; revenue tasks usually are not. Software testing probably has more excise tasks than any other aspect of software development. Maintaining test scripts, rerunning tests, and comparing expected results with actual results are all common excise tasks that routinely use large amounts of test engineers’ time. Automating excise tasks serves the test engineer in many ways. First, eliminating excise tasks eliminates drudgery, thereby making the test engineer's job more satisfying. Second, automation frees up time to focus on the fun and challenging parts of testing, such as test design, a revenue task. Third, automation allows the same test to be run thousands of times without extra effort in environments where tests are run daily or even hourly. Fourth, automation can help eliminate errors of omission, such as failing to update all the relevant files with the new set of expected results. Fifth, automation eliminates some of the variance in test quality caused by differences in individual's abilities.