```ruby
require 'spec_helper'

describe Cathode::Resource do
  describe '.new' do
    context 'with a nonexistent resource' do
      subject { Class.new(Cathode::Base) { resource :boxes, actions: [:all] } }

      it 'raises an error' do
        expect { subject }.to raise_error(Cathode::UnknownResourceError)
      end
    end

    context 'with an existing resource' do
      before do
        Rails::Application.class_eval 'class Product < ActiveRecord::Base; end'
      end

      subject { Class.new(Cathode::Base) { resource :products, actions: [:all] } }

      it 'creates a controller' do
        subject
        expect(Cathode::ProductsController).to_not be_nil
      end
    end
  end
end
```

Test against the actual resource instantiation method
user
```ruby
require 'spec_helper'

describe Cathode::Resource do
  describe '.new' do
    context 'with a nonexistent resource' do
      subject { Cathode::Resource.new(:boxes, [:all]) }

      it 'raises an error' do
        expect { subject }.to raise_error(Cathode::UnknownResourceError)
      end
    end

    context 'with an existing resource' do
      subject { Cathode::Resource.new(:products, [:all]) }

      it 'creates a controller' do
        subject
        expect(Cathode::ProductsController).to_not be_nil
      end
    end
  end
end
```
assistant