How many tests are enough?
There is no simple answer to this question; it depends on your goals and on the available resources. What is most important is that you get the optimal coverage for the goals you have set with the resources you can apply. Coverage measurement involves partitioning the specification in some manner and then measuring or estimating the extent to which each area of the specification has been tested. There are many ways to partition a specification: by feature, language elements, logical sections, testable assertions, or even paragraphs or pages. Once you determine how to partition the specification, you can define your coverage goals. Coverage measurements can be expressed in both breadth and depth terms. Breadth measurements are relatively simple to derive, since they are expressed in terms of the ratio of tests to specification features. (For example, the percentage of language elements or testable assertions that are covered by at least one test.) Depth measurements are more subjective,
