It's hard to test this Ember-Data Serializer

application_serializer.js

import DS from "ember-data";

function ensureRoot(rootName, payload) {
  var result;

  if (payload[rootName] == null) {
    result = {};
    result[rootName] = payload;
  } else {
    result = payload;
  }

  return result;
}

function ensureID(rootName, payload, requestedID) {
  if (payload[rootName].id == null) {
    payload[rootName].id = requestedID;
  }
  return payload;
}

export default DS.ActiveModelSerializer.extend({
  extractSingle: function(store, type, payload, id, requestType) {
    payload = ensureRoot(type.typeKey, payload);
    payload = ensureID(type.typeKey, payload, id);
    return this._super(store, type, payload, id, requestType);
  }
});

summary.md

My ApplicationSerializer inherits from DS.ActiveModelSerializer, which in turn inherits from DS.RestSerializer

Thus, my extractSingle overrides and calls this one, which is pretty thorny. Most notably, if I want to stub store, I need

• store.modelFactoryFor -- returns an Ember.Object subclass
• store.modelFor -- returns a complex key object, the structure of which does not seem to be publicly documented
• store.serializerFor -- maybe returns an instance of my serializer?
• store.push, which I could probably have be a no-op since I don't care about side-loads
• store.pushMany (called if there are relationships), ibid