anchor.diff:  (test file-path.absolute.12
     (is-file-path (file-path "/a/b" :as-directory t :expand-user t)
                   ((:absolute "a") "b")))
  ++
   
   (test file-path.expand-user.1
     (is-file-path (file-path "~root" :expand-user nil)
  
positive.code: (test file-path.root.4
    (is-file-path (file-path "/" :as-directory t :expand-user t)
                  ((:absolute) nil)))
  
  (test file-path.relative.1
    (is-file-path (file-path "a")
  
negative.code: (test file-path.relative.12
    (is-file-path (file-path "a/b" :as-directory t :expand-user t)
                  ((:relative "a") "b")))
  
  
  (test file-path.absolute.1
    (is-file-path (file-path "/a")
  