Created: 2012-03-19 08:23
Updated: 2018-12-13 01:58

Bond CircleCI Status

Bond is a spying and stubbing library, primarily intended for tests.

[circleci/bond "0.3.1"]
  (:require [bond.james :as bond :refer [with-spy]]))

(defn foo [x]
  (let [shaken (with-out-str (prn :martini))]

(defn bar [y]
  (foo y))

(deftest foo-is-called
  (with-spy [foo]
    (bar 2)
    (is (= 1 (-> foo bond/calls count)))))

Bond provides one main macro, with-spy. It takes a vector of defn vars (vars that resolve to fns). Each var will be redefined for the scope of the macro, wrapping the function to track arguments and call counts. At any point during the scope, you can call (bond/calls f), where f is a spied fn. calls returns a seq of maps, one for each call to fb. Each map contains the keys :args, a seq of args the fn was called with, and one of :return or :throw.

Bond also provides with-stub!. It works the same as with-spy, but redefines the function to return (constantly nil) (default), while also spying on it. This is generally preferable to Clojure's built-in with-redefs macro since it will throw an exception if the mocked function is called with the wrong number of arguments. You can specify an arbitrary function instead of the default (constantly nil) by providing a [fn-var replacement-fn] vector in place of just the fn name:

  (:require [bond.james :as bond :refer [with-stub!]]))

(defn foo [x] ...)

(defn bar [y] ...)

(deftest foo-is-called
  (with-stub! [[foo (fn [x] "foo")]
               [bar (fn [y] "bar")]]
    (is (= ["foo" "bar"] [(foo 1) (bar 2)]))))
(deftest consecutive-stubbing
  (with-stub! [[foo [(fn [x] "foo1") 
                     (fn [x] "foo2") 
                     (fn [x] "foo3")]]
               [bar (fn [y] "bar")]]
    (is (= ["foo1" "foo2" "foo3" "bar"] [(foo 1) (foo 1) (foo 1) (bar 2)]))))

Private functions can also be stubbed or spyed:


(defn- foo [x] ...)
  (:require [bond.james :as bond :refer [with-stub!]]
            [ :as foo]))

(deftest foo-is-called
  (with-stub! [[foo/foo (fn [x] "foo")]]
    (is (= "foo" (#'foo/foo 1)))
    (is (= [1] (-> #'foo/foo bond/calls first :args)))))

There is also a with-stub macro which works like with-stub! but omits the argument check.

In addition to with-spy and with-stub!, Bond also provides with-spy-ns and with-stub-ns which can spy/stub every function in a namespace in one go:

  (:require [bond.james :as bond]
            [clojure.test :refer (deftest is)]))

(defn foo [] :foo)

(defn bar [] :bar)

(deftest you-can-stub-entire-ns
  (is (= :foo (foo)))
  (is (= :bar (bar)))
  (bond/with-stub-ns [[foo (constantly :baz)]]
    (is (= :baz (foo)))
    (is (= :baz (bar)))))


Distributed under the Eclipse Public License.

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