Now we will look at the test tools, or special tools that are used: one of them are the test drivers. These are basically the environment in which the components or the units or models are tested. It is very interesting and very important for the bottom-up testing. The other tests are: when you are testing, you are expecting a certain component to be ready, so that you can just test it. But when such a component has to become structured, what you can do, you can simulate the function of the component which has to be prepared and then it is put in the environment as a test driver and then you test it. So, this could be useful for the top-down testing.
Then you have the test data generators. These are automatic test data generators. If a skeletal frame work is used with dummy functional modules, then the skeleton becomes the test driver.