Unit Test Boundaries

One principle to follow when writing a unit test is that a unit test should ideally not cross boundaries . Michael Feathers takes a harder stance in saying. A test is not a unit test if: It talks to the database It communicates across the network It touches the file system It can't run at the same time as any of your other unit tests You have to do special things to your environment (such as editing config files) to run it Tests that do these things aren't bad. Often they are worth writing, and they can be written in a unit test harness. However, it is important to be able to separate them from true unit tests so that we can keep a set of tests that we can run fast whenever we make our changes. Speed isn't the only benefit of following these...(read more)

Source Click Here.