在Clojure中重新绑定随机数生成器 [英] Re-bind a Random Number Generator in Clojure

问题描述

我在Clojure中有一个函数，通过 rand 生成随机数：

I've got a function in Clojure which generates random numbers via rand:

core.clj ：

(ns my-lib.core)

(def my-rand rand)

(defn my-fn []
  (take 3 (repeatedly my-rand)))

我想测试一下，但很难，因为我不知道该怎么做。有没有办法，我可以重新绑定 core / my-rand ，使它使测试更容易？像这样：

I'd like to test it, but it's hard since I don't know what to expect. Is there a way that I could re-bind core/my-rand such that it makes testing easier? Something like this:

core_test.clj ：

(ns my-lib.core-test
  (:require [clojure.test :refer :all]
            [my-lib.core as core]))

; i'd like to re-bind the my-rand function here to make testing easier, but this doesn't work
(def core/my-rand (constantly 1))

(deftest my-fn
  (is (= (core/my-fn) '(1 1 1))))

推荐答案

您需要 with-redefs ：

http://clojuredocs.org/clojure_core/clojure.core/with-redefs

(deftest my-fn-test
  (with-redefs [core/my-fn (constantly 1)]
    (is (= (repeatedly 3 core/my-fn) '(1 1 1)))))

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