Assume I have src/cljc/a/b/c.cljc. If I navigate in dired to test/cljc/a/b and then C-x C-f new_test.cljc then a new buffer is helpfully created (ns cljc.a.b.new_test) (filed in #310). However, it also requires:
(:require [cljc.a.b.new :refer :all]
[clojure.test :refer :all])
(In terms of style I would suggest it is actually [a.b.new :as sut] for consistency, but that is a personal style issue).
Namespaces are setup correctly so src/cljc is a source path and test/cljc is a test path according to project.clj.
Libraries are Clojure 1.7.0 and snapshot cider.