vcr-clj is a general function recording/playback library for Clojure. It is intended to be used when testing code that does I/O, to achieve several goals:
Any clojure function (er, var) can be recorded and played back.
vcr-clj requires Clojure 1.4 or later.
[com.gfredericks/vcr-clj "0.4.16"]
An example with clojure.test
:
(ns my.project-test
(:require [clojure.test :refer :all]
[vcr-clj.core :refer [with-cassette]]))
(deftest here-is-my-test
(with-cassette :foo [{:var #'my.io.ns/get-data, ...extra options...}]
... do some testy things ...
... that call my.io.ns/get-data ...))
There is also currently a separate namespace for recording clj-http
requests
in particular:
(ns my.project-test
(:require [clojure.test :refer :all]
[vcr-clj.clj-http :refer [with-cassette]]))
(deftest here-is-my-webby-test
(with-cassette :foo
... do some testy things ...
... that call clj-http functions ...))
(deftest this-test-only-records-some-calls
(with-cassette {:name :foo-2
:recordable? (fn [req] (worth-recording? req))}
... do some testy things ...
... that call clj-http functions ...))
The first time you run a with-cassette
block, a cassette file is
created in the /cassettes
directory. Each subsequent time, playback
is performed using the cassette in the directory. You can delete it to
force a re-record.
Namespaced keywords can be used to group cassettes in the filesystem.
Each var that is recorded can be customized with options:
:arg-transformer
: A function with the same argument signature as the
recorded function, which returns a vector of possibly transformed arguments.
During recording/playback, the original arguments to the function call are
passed through this transformer, and the transformed arguments are passed to
arg-key-fn
, recordable?
and the recorded function. This can be useful for
replacing an argument that would be destructively consumed (e.g. a mutable
InputStream
) with an indestructible substitute. The transformed arguments
ought to be equivalent to the original arguments for the purpose of the code
under test. The default is clojure.core/vector
, which just passes along
the original arguments.:arg-key-fn
: A function with the same argument signature as the recorded
function, which returns a value for "fingerprinting" the arguments to each
call. During recording, the value returned by this function will be saved
along with the recorded call in the cassette. During playback, the value
returned by this function will be used to look up a matching recorded call in
the cassette. The default is clojure.core/vector
, which just compares the
arguments as given.:recordable?
: A function with the same argument signature as the recorded
function, which returns truthy or falsy. If it returns falsy, the call will
be passed through to the original function during both recording and
playback. The default is clojure.core/identity
.:return-transformer
: A single-argument function that takes a value returned
by the recorded function and returns a transformed return value. During
recording, the recorded function will be composed with this transformer
function. This can be useful for ensuring serializability. The transformed
return value ought to be equivalent to the original return value for the
purpose of the code under test. The default is clojure.core/identity
.Copyright (C) 2012 Gary Fredericks
Distributed under the Eclipse Public License, the same as Clojure.
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