Ok, you can look at tit this way.... terminate heat call, would imply write 0 to P1.0.
So now you have, Write 1 to P1.0, then check for the W signal, If it is on, then proceed and write 0 to P1.0. If 0 gets written to P1.0, then it passes, or fails.
I can tell you one more thing, the W signal, the P1.0 signals all have LEDs connected on my interface. So I can visually see whats happening.
And also all this is being done to test thermostats