Ever since they introduced the testability framework in 2009, Microsoft have been building on their application test collateral. As already pointed out in Chapter 3, The Test Tool and Standard Tests, it contains an immense number of tests. These tests cover the whole standard application, from financial management, sales and purchase, through warehouse and manufacturing, to service management. With every major release or cumulative update, new tests have been and will continue to be added to cover new features and recent bug fixes. Years of work we all can profit from. If your code extends the standard application, what will be the impact of it on the standard application?

You could go about writing your own tests. You could also choose to run the standard tests and see the results. And, of course, in the end, you could do both, as your extension most...