On Repl-Driven Programming(mikelevins.github.io)

  (defparamater *db* (connect-to-test-db))
  (query-db *db* (make-query some-query-description))
  ;; see that it pulls out the desired record
  (let ((record (query-db *db* (make-query sqd)))
    (update-record record)
    (write-to-db *db* record)) ;; update the entry
  ;; rerun the query above to see that things changed as expected
  ;; rewrite that let as a defun:
  (defun make-update-to-some-record (sqd db)
    (let ((record ...))
      ...))
   ;; test that it works
   (make-update-to-some-record sqd *db*)
   ;; see that it does in fact do the same as the let above.
   ;; move that to a permanent source file, and build it
   ;; into the system.
   ;; move tests into test file.
   ;; repeat with next feature/task

    The Squeak/Smalltalk programming system consists of three parts:

    * a virtual machine for your platform,
    * both image and changes files of a particular version, and
    * a sources file for the particular image file.