@domcleal,  overridable_lookup_keys is the method used in the partial views/puppetclasses/_class_parameters.html.erb that is rendered by the puppetclasses_controller#parameters method.  overridable_lookup_keys is defined in LookupKeysHelper.

I'm checking that the correct number of "overridable" lookup keys for the given puppetclass rendered by the form.  In the tests, it's either 1 or 2 depending on the situation.