anchor.diff:    (multiple-value-bind (x y) (split-at 1 (list 1 2 3))
       (is (and (equal x (list 1))
                (equal y (list 2 3))))))
  +
  +(deftest test-insert ()
  +  (is (eq nil (insert nil nil :test nil)))
  +  (is (equal (range 1 10)
  +             (let ((xs (list 3 6 10 7 4 1 8 2 9 5))
  +                   (ys nil))
  +               (dolist (x xs ys)
  +                 (setf ys (insert x ys)))))))
   
   (deftest test-starts-with ()
     (is (eq t (starts-with "Hello, world!" "Hell")))
  
positive.code: ;;; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  ;;; DEALINGS IN THE SOFTWARE.
  
  (defpackage :com.superadditive.incf-cl-tests
    (:nicknames :incf-cl-tests)
    (:use :common-lisp :incf-cl :stefil)
  
negative.code:      (is (equal x (list 1 1 1 3 5)))
       (is (equal y (list 6 8))))))
  
  (deftest test-break ()
    (multiple-value-bind (x y) (break* #'oddp (nreverse (list 1 1 1 3 5 6 8)))
      (is (equal x (list 8 6)))
      (is (equal y (nreverse (list 1 1 1 3 5))))))
  
  (deftest test-split-at ()
    (is (eq (split-at -10 (list 1 2 3)) nil))
    (is (eq (split-at 0 nil) nil))
  