At the beginning of this book, we looked at test reusability as a strategy for enhancing maintenance. We tried to minimize duplicating the same functionality in multiple tests and even in the constituent steps. The test maintainability topic was frequently present in the examples throughout this book mainly because of how much it affects test durability and effectiveness over time in addition to how much it lowers the automation cost. The simplest scenario which describes all the aforementioned characteristics is when having the login functionality implemented inside a number of tests. If at some point in time the login window is redesigned to allow the choice between Windows or regular member authentication before being able to input the credentials, then all the automated login functionality scattered among the tests should also change! Hence, your tests:
Lack durability, since they are vulnerable to changes outside the functionality they are testing
Lack effectiveness, since...