Something like this https://github.com/BenjaminMedia/image_system/blob/bc1366d4dfe28d26882d1867e15a14df858a1556/spec/lib/image_system/cdn/communication_system_spec.rb#L103-L107

Eg 

```ruby
res = subject.download(aspect: "something") # no crop
expect(res).to_not include("crop")