Completed coverage and refactored to make testable

project.clj

@@ -3,4 +3,4 @@
   :url "http://example.com/FIXME"
   :license {:name "Eclipse Public License"
             :url "http://www.eclipse.org/legal/epl-v10.html"}
-  :dependencies [[org.clojure/clojure "1.5.1"]])
+  :dependencies [[org.clojure/clojure "1.8.0"]])

src/ffmpeg_clj/core.clj

@@ -1,27 +1,28 @@
 (ns ffmpeg-clj.core
-  (:require 
-   [clojure.java.shell :refer [sh]]
-   [clojure.string :as s]))
+    (:require
+      [clojure.java.shell :refer [sh]]
+      [clojure.string :as s]))
 
 (def ^:dynamic *bin* "ffmpeg")
 
-(defn cmd [& argv] 
-  (->> argv
-       (map #(if (keyword? %) (str "-" (name %)) (str %)))
-       (into [*bin*])))
+(defn create-cmd-string-seq [& argv]
+      (->> argv
+           (map #(if (keyword? %) (str "-" (name %)) (str %)))
+           (into [*bin*])))
 
-(defn bin [] *bin*)
+(defn ffmpeg-factory [shell-call-fn]
+      (fn [& args]
+          (let [cmd! (apply shell-call-fn (apply create-cmd-string-seq args))
+                {:keys [exit out err]} cmd!]
+               (when-not (zero? exit)
+                         (throw
+                           (Exception. err)))
+               out)))
 
-(defn ffmpeg! [& args]
-  (let [cmd! (apply sh (apply cmd args))
-        {:keys [exit out err]} cmd!]
-    (when-not (zero? exit)
-      (throw
-       (Exception. err)))
-      out))
+(def ffmpeg! (ffmpeg-factory sh))
 
-(defn version [] 
-  (as-> (ffmpeg! "-version") o
-        (re-find #"version \S+" o)
-        (s/split o #" ")
-        (last o)))
+(defn version []
+      (as-> (ffmpeg! "-version") o
+            (re-find #"version \S+" o)
+            (s/split o #" ")
+            (last o)))

test/ffmpeg_clj/core_test.clj

@@ -1,7 +1,35 @@
 (ns ffmpeg-clj.core-test
-  (:require [clojure.test :refer :all]
-            [ffmpeg-clj.core :refer :all]))
+    (:require [clojure.test :refer :all]
+      [ffmpeg-clj.core :refer :all]
+      [clojure.string :as s]))
 
-(deftest a-test
-  (testing "FIXME, I fail."
-    (is (= 0 1))))
+(deftest cmd-creates-command-with-only-ffmpeg-when-no-args-provided
+         (testing "If no args are provided to (cmd) it should create a list with only the command in it (\"ffmpeg\")."
+                  (is (= (create-cmd-string-seq) ["ffmpeg"]))))
+
+(deftest cmd-creates-command-with-one-option-and-one-value
+         (testing "A ffmpeg call with an option (using a - before) from a keyword and a value from a string should be created."
+                  (is (= (create-cmd-string-seq :codec "h264") ["ffmpeg", "-codec", "h264"]))))
+
+(deftest cmd-combination-of-many-keywords-and-values
+         (testing "Keywords must be seen as options for ffmpeg and string values as parameters"
+                  (is (= (create-cmd-string-seq "value1" :option1 "value2" "value3" :option2 "value4" :option3 :option4) ["ffmpeg", "value1", "-option1", "value2", "value3", "-option2", "value4", "-option3", "-option4"]))))
+
+
+(defn mocked-sh
+      "A mocked sh function that return a map with the result values as in the arguments"
+      [exit-code stdout err]
+      (fn [& arguments-ignored-in-this-mock]
+          {:exit exit-code :out  stdout :err err}))
+
+(deftest ffmpeg-clj-when-exit-code-from-sh-call-is-not-zero-throws-err-as-exception
+         (testing "Should throw the error of the shell call if the exit code is not 0"
+                  (is (thrown? Exception ((ffmpeg-factory (mocked-sh 1 nil "Error")) "irrelevant_value")))))
+
+(deftest ffmpeg-clj-when-exit-code-from-the-sh-is-zero-returns-the-out-value-call
+         (testing "Should return the output of the shell call if the exit code is 0"
+                  (is (= ((ffmpeg-factory (mocked-sh 0 "Test stdout value" nil)) "irrelevant_value") "Test stdout value"))))
+
+(deftest ffmpeg-version
+         (testing "Test the version of ffmpeg"
+                  (is (not (s/blank? (version))))))