A common question during a job interview for test automation is "How do you plan to build the test suite?" When I was new to software test automation, I would answer that 99 percent coverage is critical. After reality had a chance to catch up, it became apparent that such high coverage is impossible due to obvious time constraints.

Instead of having 100 percent test coverage, the best that can be done is to prioritize the growth of the test suites. In this section, we will discuss the order in which test suits should be built. As we build our test suites, some tests will cross multiple boundaries, which is perfectly normal. However, it is best to have a way to group certain tests together so they can be executed individually. For example the smoke test suite is a subset of the regression suite, but we need ability to execute it without having to run the regression suite.