mirage.js

//mirage/config.js
export default function() {
  this.get('/tenants/current', (schema, request) => {
    /*
    returns:
      {
        tenant: {
          id: 1
          profileId: 1
        }
      }
    expecting:
      {
        tenant: {
          id: 1,
          profileId: 1
        },
        profiles: [{
          id: 1
        }]
      }
    */
    return {
      tenant: schema.tenants.first()
    }
  });
}

//mirage/models/tenant.js
export default Model.extend({
  profile: belongsTo()
});

//mirage/models/profile.js
export default Model.extend({
});

//mirage/serializers/application.js
import { ActiveModelSerializer } from 'ember-cli-mirage';
export default ActiveModelSerializer.extend({
});


//mirage/serializers/tenant.js
import ApplicationSerializer from './application';
export default ApplicationSerializer.extend({
  include: ['profile']
});

// mirage/scenarios
export default function(store) {
  var profile = store.create('profile');
  store.create('tenant', {
    profile: profile
  });
}

Maybe i can help. Can you please explain in a little bit more detail what you are trying to do and what is going wrong?

@kgish I am creating a profile and a tenant and assigning the profile to the tenant when it is created. with the "include" in the tenant serializer, I am expecting to get the profile data back when I call tenant: schema.tenants.first(), but I think because this relationship is syncronous in my ember data model, I need to also include the profile data as well. Unsure.