anchor.diff:  
     (setf (gethash 8 table-of-cube-roots) 2)
     (setf (gethash -27 table-of-cube-roots) -3)
  -  (assert-equal ___ (gethash -3 table-of-cube-roots))
  -  (assert-equal ___ (hash-table-count table-of-cube-roots))
  +  (assert-equal nil (gethash -3 table-of-cube-roots))
  +  (assert-equal 3 (hash-table-count table-of-cube-roots))
   
     "accessing unset keys returns nil"
  -  (assert-equal ___ (gethash 125 table-of-cube-roots))))
  +  (assert-equal nil (gethash 125 table-of-cube-roots))))
   
   
   (define-test test-hash-key-equality
  
positive.code:       (setf (gethash "two" expected) "zwei")
  
        (setf (gethash "one" babel-fish) "ein")
        (setf (gethash "two" babel-fish) ____)
  
        (assert-true (equalp babel-fish expected))))
  
  
negative.code:       (setf (gethash "one" h2) "yat")
        (setf (gethash "two" h1) "yi")
        (setf (gethash "two" h2) "yi")
        (true-or-false? nil (eq h1 h2))
        (true-or-false? nil (equal h1 h2))
        (true-or-false? t (equalp h1 h2))))
  
  
  (define-test test-changing-hash-tables
  