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zombie

A Clojure framework for declarative semantic data transformation. Sometimes during testing, concrete values don't matter. All that matters is semantics. Capture the essence of your test cases with zombie. See below for usage.

Installation

Add the following to your :dependencies

[zombie "0.2.1"]

Usage

I'll motivate the usage by first demonstrating zombie's full power. Later we'll break it down. Let's say I have a function:

(defn alcohol-legal [people]
  (filter #(>= (:age %) 21) people))

I could write a test such as:

(deftest mike-is-legal
  (let [mike {:name "Mike" :age 21}
        pete {:name "Pete" :age 18}]
    (is (= [mike] (alcohol-legal [mike pete])))))

But what's the essence of the test? Does Pete's name matter? Does the fact that he's exactly 18 matter? Nope. All the matters is that there's someone else that's under 21. Declarative semantic transformations do this better.

(deftest mike-is-legal
  (spawn {}
         [mike {:name "Mike" :age 21}
          _    (is-like mike (but-he (has-a-lesser :age)))]
    (is (= [mike] (alcohol-legal zombies)))))

A little session at the REPL shows how to leverage Zombie to make new data.

user=> (def mike {:nickname "Dro"})
#'user/mike
user=> (def john (is-like mike (but-he (has-a-different :nickname))))
#'user/john
user=> mike
{:nickname "Dro"}
user=> john
{:nickname "{xl#X:YnO%5(YH@A2Zwg)rcM8x@}U|$%F"}
user=> (def mike {:age 21})
#'user/mike
user=> (def john (is-like mike (but-he (has-a-different :age))))
#'user/john
user=> mike
{:age 21}
user=> john
{:age 54N}

Data can be "modeled" with the following functions:

is-like
but-it
but-he
but-she

Data can be manipulated with the following functions:

has-a-different
has-a-smaller
has-a-lesser
has-no
has-a-nil
has-a
has-an-earlier
has-a-later

Time can be manipulated. Here I use the testing framework Midje:

(fact
 (let [mike {:birthday (time/date-time 1991 1 13)}
       owen (is-like mike (but-he (has-an-earlier :birthday)))]
   (time/before? (:birthday owen) (:birthday mike)))
 => true)

Spawning

The spawn function allows access to all the declared vars via a var named 'zombies'. Data can then be anonymously named. spawn is made to feel like the let form. However, it does not support destructuring.

(spawn
 {} ; Options, explained below
 [my-expectations {:grade :A}
  _               {:grade :B}
  _               {:grade :C}]
 (do
   (fact (count zombies) => 3)
   (fact (apply not= zombies) => true)))

Check out the tests for more examples.

Options

spawn takes an options map as it's last parameter for runtime configurability.

:n

The number of tests to run. The data will be different each time. Defaults to 1.

:mode

The mode to run spawn in. The default mode is :quiet. The :loud mode writes the data used for each test to the console.

:aggregate

Configure the name for the aggregate var. Defaults to zombies.

Example

(spawn
 [mike {:age 21}
  owen (is-like mike (but-he (has-a-different :age)))]
 (do
   (fact (:age mike) =not=> (:age owen))
   (fact [mike owen] => all-the-vars))
 {:n 50 :mode :loud :aggregate all-the-vars})

This will run 50 facts, where the :age of owen is different each time, but always obeying the rule that it never equals (:age mike).

Perhaps more clearly at the REPL:

user=> (spawn [mike {:name "Mike"} owen (is-like mike (but-he (has-a-different :name)))] (do) {:n 5 :mode :loud})
===================================
Test case  0
===================================
([mike {:name Mike}] [owen {:name c.gwb3pGO<{^!gC}])
===================================
Test case  1
===================================
([mike {:name Mike}] [owen {:name c8NTSxrs9EP&yC5M2#Q[yl7F-C`A}?<XPX:\{\|&&5r=U}])
===================================
Test case  2
===================================
([mike {:name Mike}] [owen {:name UlmmpI5{j'y4C2v<N/L]3I0^*}])
===================================
Test case  3
===================================
([mike {:name Mike}] [owen {:name z0YQy7iv[/nDKGxui}])
===================================
Test case  4
===================================
([mike {:name Mike}] [owen {:name C(l{Ajbvz-`|O}])
nil

Extending the API

For functions such as has-no and has-a-different, the API can be extended to dispatch to specific types. Suppose you wanted an implementation of has-no to work on a map:

(extend-type clojure.lang.PersistentArrayMap
  Morph
  (identity-element
   [this description attribute]
   (assoc description attribute {})))

Then you could do:

(fact
 (let [mike {:grades {:math :B :science :A :english :A}}
       some-dude (is-like mike (but-he (has-no :grades)))]
   (empty? (:grade some-dude)))
 => true)

Contribute

Have a function in mind to mold data or extend the API in a good direction? Fork this and pull request, because I probably want it.

To do

  • More data manipulation functions (has-a-greater, has-in-range, has-any-positive-integer, etc)
  • Exclude Midje from the README. It'll make reading this doc much easier
  • Let spawn take no options and use defaults, or read from a config file

License

Copyright © 2012 Michael Drogalis

Distributed under the Eclipse Public License, the same as Clojure.

Thanks

Special thanks to RJMetrics for letting me open-source this project. I developed this library while working there.

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