Create spec/app\_spec.rb and put the following in it:
```ruby
require 'sinatra'
require 'spec/interop/test'
require 'sinatra/test/unit'
require 'app'
require 'test/spec'
set :environment, :test
describe 'The HelloWorld App' do
before(:each) do
set :views => File.join(File.dirname(__FILE__), "..", "views")
end
it "says hello" do
get '/'
response.should.be.ok
response.body.should.equal 'Hello World'
end
end
```
Then run the test:
```ruby
spec spec/app_spec.rb
```