How to mock an Ember-CLI service in an acceptance test?

Short version of the solution: your registered mock service must have a different service:name than the “real” service you’re trying to mock.

Acceptance test:

import Ember from 'ember';
import { module, test } from 'qunit';
import startApp from 'container-doubling/tests/helpers/start-app';

var application;

let speakerMock = Ember.Service.extend({
  speak: function() {
    console.log("Acceptance Mock!");
  }
});

module('Acceptance | acceptance demo', {
  beforeEach: function() {
    application = startApp();

    // the key here is that the registered service:name IS NOT the same as the real service you're trying to mock
    // if you inject it as the same service:name, then the real one will take precedence and be loaded
    application.register('service:mockSpeaker', speakerMock);

    // this should look like your non-test injection, but with the service:name being that of the mock.
    // this will make speakerService use your mock
    application.inject('component', 'speakerService', 'service:mockSpeaker');
  },

  afterEach: function() {
    Ember.run(application, 'destroy');
  }
});

test('visit a route that will trigger usage of the mock service' , function(assert) {
  visit("https://stackoverflow.com/");

  andThen(function() {
    assert.equal(currentURL(), "https://stackoverflow.com/");
  });
});

Integration test (this is what I was originally working on that caused me issues)

import { moduleForComponent, test } from 'ember-qunit';
import hbs from 'htmlbars-inline-precompile';
import Ember from 'ember';


let speakerMock = Ember.Service.extend({
  speak: function() {
    console.log("Mock one!");
  }
});

moduleForComponent('component-one', 'Integration | Component | component one', {
  integration: true,

  beforeEach: function() {
    // ember 1.13
    this.container.register('service:mockspeaker', speakerMock);
    this.container.injection('component', 'speakerService', 'service:mockspeaker');

    // ember 2.1
    //this.container.registry.register('service:mockspeaker', speakerMock);
    //this.container.registry.injection('component', 'speakerService', 'service:mockspeaker');
  }
});

test('it renders', function(assert) {
  assert.expect(1);

  this.render(hbs`{{component-one}}`);

  assert.ok(true);
});