In software validation how do you call testing a software with itself?

In order to test a function (let's say it's write_gpio()), I could use an oscilloscope.

But no, I'm testing it with another board which has the same software at the same version and where i'm doing a read_gpio().

Is there a name to differentiate the two technics?

I am testing embedded systems, but I reckon it could be appliable to desktop applications where we can run different software instances. However, it remains more relevant on embedded systems.