find_src.el

(defun src-full-path (project-root file-name)
  (concat
   (replace-regexp-in-string
    (concat (expand-file-name project-root) "test/clojure/expectations")
    (concat project-root "src/clojure")
    (file-name-directory file-name))
   (replace-regexp-in-string
    "_expectations"
    ""
    (file-name-nondirectory file-name))))

(defun find-src ()
  (interactive)
  (let* ((project-root (locate-dominating-file 
                         (file-name-directory (buffer-file-name)) "project.clj")))
    (if project-root
        (let* ((full-path (src-full-path project-root (buffer-file-name))))
          (if (file-exists-p full-path)
              (set-window-buffer (next-window) (find-file-noselect full-path))
            (message (concat "cound not find " full-path))))
      (message (concat "no project.clj found at or below " (buffer-file-name))))))