principle & function testing

[Peter]

Hello, what is the difference between 'principle & functional' testing?

PJW would be able to give you a better definition than me, but essentially, functional testing is checking that something performs at it is expected to in response to a set of control inputs, principles testing is making sure that it does what it does when it is supposed to do it. Another way of looking at it is that the functional testing checks that it has been built right, principles testing checks that the right thing has been built.

For example, functional testing of a set of points will make sure that the points move normal when the relevant relays are up, and when it is there, the right detection relays are in place. Principles testing would test that the points only move when the conditions are right, that other things cannot happen when the points are not in the position they should be.