App: Sinatra + ActiveRecord  

Trying to test association existence using best practices.  

I really like the Shoulda syntax:

```
    describe Bar do
      it { should belong_to(:foo) }
    end

```

However, RSpec cannot seem to find the `belong_to` method.

```
    1) ResOutcome 
       Failure/Error: it { should belong_to(:foo) }
       NoMethodError:
         undefined method `belong_to' for #<RSpec::Core::ExampleGroup::Nested_1:0x00000103ac6760>
       # ./spec/models/bar_spec.rb:48:in `block (2 levels) in <top (required)>'

```

Any hints?  

Does Shoulda association testing only work in Rails apps (with rspec-rails)?  

Thank you all for your time.