adding decoder test

test/helper.rb

@@ -0,0 +1,15 @@
+require 'md5'
+require 'test/unit'
+require 'icanhasaudio'
+require 'tempfile'
+
+%w(../lib ../ext).each do |path|
+  $LOAD_PATH.unshift(File.expand_path(File.join(File.dirname(__FILE__), path)))
+end
+
+module ICANHASAUDIO
+  class TestCase < Test::Unit::TestCase
+    MP3_FILE = File.dirname(__FILE__) + "/assets/icha.mp3"
+    undef :default_test
+  end
+end

test/mpeg/test_decoder.rb

@@ -0,0 +1,20 @@
+require File.expand_path(File.join(File.dirname(__FILE__), '..', 'helper'))
+
+module Audio
+  module MPEG
+    class TestDecoder < ICANHASAUDIO::TestCase
+      def setup
+        @decoder = MPEG::Decoder.new
+      end
+
+      def test_decode
+        out = "#{Dir::tmpdir}/out.wav"
+        File.open(out, 'wb+') { |outfile|
+          @decoder.decode(File.open(MP3_FILE, 'rb'), outfile)
+        }
+        digest = Digest::MD5.hexdigest(File.read(out))
+        assert_equal '9a55bcdda77ec7c20f32031632927403', digest
+      end
+    end
+  end
+end