(assert (equal (stable-sort (list 1 2 3 -3 -2 -1) '< :key 'abs)
'(1 -1 2 -2 3 -3)))
+;;; CSR broke FILL by not returning the sequence argument in a transform.
+(let* ((s1 (copy-seq "abcde"))
+ (s2 (fill s1 #\z)))
+ (assert s2)
+ (assert (string= s2 "zzzzz")))