First install the RSpec and ZenTest gem:
```ruby
$ sudo gem install rspec zentest
```
Next create the spec folder:
```ruby
$ cd project_folder
$ mkdir spec
```
Save the following to **spec/helper.rb**:
```ruby
$LOAD_PATH.unshift File.dirname(__FILE__) + '/..'
require 'rubygems'
require 'spec'
#require 'spec/rake/spectask' not needed, because ZenTest supports rspec now
```
Now create **spec/transcoder\_spec.rb**, and add the following test to it:
```ruby
require File.dirname(__FILE__) + '/helper'
require File.dirname(__FILE__) + '/../transcoder.rb'
context "Transcoder" do
setup do
# Setup your stuff here
end
it "should support 3gp format" do
Transcoder.convert("me_and_you.3gp").should == true
end
end
```
Let's not forget the class we're testing, put this code in **lib/transcoder.rb**:
```ruby
class Transcoder
def initialize
end
def self.convert(file)
return true
end
end
```
Note that autotest automatically looks for your code in the lib folder.
Now run the test with the zentest command:
```ruby
autotest
```
Change your files and autotest will run the test again.
Tip: Read [Getting started with Autotest - Continuous Testing](http://ph7spot.com/articles/getting_started_with_autotest) and [Setting up autotest to use Growl on OSX](http://wincent.com/knowledge-base/Setting_up_autotest_to_use_Growl) for more information on how to increase your productivity.