core.clj

(ns depr.core)

(defn ^:private !! [c]
  (println "WARNING - Deprecation of " c " in effect."))

(defmacro defn-deprecated 
  [nom _ alt ds & arities]
  (let [silence? (:silence-deprecations (meta clojure.core/*ns*))]
    (when-not silence?
     (!! alt)))              
  `(defn ~nom ~ds ~@arities))

core_test.clj

(ns ^:silence-deprecations depr.core-test
  (:use clojure.test)
  (:require [depr.core :refer (defn-deprecated)]))

(defn-deprecated foo :as quux
  "Does something"
  []
  42)

(deftest a-test
  (testing "Nothing really"
    (is (= 42 (foo)))))