rapid_check_testable_base.hs

-- Property is trivially convertible to Property
instance Testable Property where
  property = id

-- Result is convertible to Property by creating
-- a generator that always return this same result
instance Testable Result where
  property r = Property (Gen (const r))

-- Bool can be converted to Result
-- Result can be converted to a Property
-- By composition we get that Bool is convertible to Property
instance Testable Bool where
  property = property . toResult where
      toResult b = if b then Success
                        else Failure { seed = 0, counterExample = []}