[RFC] tests in test/dm/video.c are not independent

Hello Simon,

looking at the tests in test/dm/video.c it seems that none of them clears the screen before adding text and testing the hash of the frame buffer. So it is hard to tell which output led to changes in subsequent tests.

I think the tests should first clear the screen to start from a defined state. This will make the tests independent of each other.

What is your view?

Best regards

Heinrich