Adding clear() command won't help as is, because d3d12 runner will clear unconditionally. For now I removed that unconditional clear, please take a look.
Another option is to clear once, if it's really necessary. For example right on [test] section. That will have to touch all runners, but at the same time, d3d9/d3d11 ones do not clear already and somehow it's not a problem.
Oh, right. I don't think we want to clear before every draw, no. There may be an argument for clearing at the start of each test, although I think that in that case we'd like to clear with something other than zeroes.