Making Testing More Effective Through Increased Testability

While there are few people who would would argue that testing is easy, it also should not be prohibitively difficult. The difficult part in testing software should be in deciding what to test, not how to test it. In a post from late September 2017, Michael Bolton describes how important testability is in the creation of a stable project with less risk of bugs at the time of delivery. If releasing a project untested or with insufficient depth of testing sounds risky to you, you are in good company. Making testing easier, known as increasing testability, allows for more thorough testing and (hopefully) a more polished, bug-free finished product.

Bolton describes testability in terms of visibility and controllability. The examples that he gives for visibility are log files and continuous monitoring. For controllability, Bolton cites application programming interfaces or APIs as the most common method for the easy manipulation of the product. An important takeaway from the post is that while it is certainly helpful to the tester if a product has things like log files and an API, this is not all that testability encompasses. Bolton presents the idea of testability as a set of relationships between multiple elements in the design process including the product, the tester, the development team, and the development environment. The overall testability of a product is a result of the complex interactions between all of these people and things involved.

The first category that Bolton mentions is epistemic testability. It is impossible for a tester to know all of the bugs in the code before performing any testing. If this were the case, there would be no need for software testers at all. The act of testing explores what Bolton calls a “risk gap,” or the areas in the project that the tester is uncertain about or unfamiliar with. Next, Bolton considers value-related testability, which refers to knowledge of what the intended user of a program is looking to gain. Understanding what is valuable to others allows a tester to focus his or her efforts where it will have the most significant impact. Intrinsic testability refers to the product’s ability to be easily understood by the tester. If a program’s behavior is easy to follow and its state is transparent to the tester, he or she will have a far easier time properly testing it. Since most projects are assigned to teams of people in many different positions, with different tools and knowledge, access to these people and resources is essential for project-related testability. Finally, subjective testability refers to the skills of the tester or testing teams matches the requirements of the project.

Bolton’s more literary definitions of testing were a welcome change from the testing material that I’ve read online and in text. Bolton seems to focus more on the people and the environment that the testing is being conducted in rather than on what specific tests are used. I think that as a student, many of the points that he makes are important to carry with me into any potential professional positions. Evaluating the testability of products through Bolton’s methods will allow me to better manage risk and deliver products with fewer bugs.

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