Cover is not yet implemented for Chiseltest

[Gallagator]

Cover statements are not yet possible. Something like:

class Foo() extends Module {
  val out = IO(Output(Bool()))
  val i = Counter(10)
  out := i === 9
  cover(out)
}

verified with:

verify((new Foo), CVC4EngineAnnotation, CoverCheck(10))

Which should generate a trace showing that it is possible for out to go high.