Found it -- disable setupEmberTesting in ember-qunit's start

Author: NullVoxPopuli

test-app/tests/test-helper.js

@@ -99,7 +99,11 @@ QUnit.assert.deprecationsInclude = function (expected) {
   });
 };
 
-start();
+start({
+  // We manage Ember.testing manually in this test-app
+  // (we probably don't need to anymore since ember-qunit handles it)
+  setupEmberTesting: false,
+});
 
 if (typeof Testem !== 'undefined') {
   Testem.hookIntoTestFramework();

test-app/tests/unit/setup-context-test.js

@@ -1,5 +1,4 @@
 import { module, test } from 'qunit';
-import { setupEmberTesting } from 'ember-qunit';
 import Service, { inject as injectService } from '@ember/service';
 import {
   setupContext,
@@ -30,15 +29,14 @@ import config from '../../config/environment';
 import Ember from 'ember';
 import { deprecate, warn } from '@ember/debug';
 
-console.log(Ember.testing);
+console.log('1', Ember.testing);
 module('setupContext', function (hooks) {
-  setupEmberTesting(hooks);
-
   if (!hasEmberVersion(2, 4)) {
     return;
   }
 
   hooks.beforeEach(function () {
+    console.log('2', Ember.testing);
     setResolverRegistry({
       'service:foo': Service.extend({ isFoo: true }),
     });
@@ -66,6 +64,7 @@ module('setupContext', function (hooks) {
   function setupContextTests() {
     module('without options', function (hooks) {
       hooks.beforeEach(function () {
+        console.log('3', Ember.testing);
         context = {};
         return setupContext(context);
       });
@@ -845,6 +844,7 @@ module('setupContext', function (hooks) {
 
   module('with only application set', function (hooks) {
     hooks.beforeEach(function () {
+      console.log('4', Ember.testing);
       setResolver(null);
       setApplication(application);
     });
@@ -854,6 +854,7 @@ module('setupContext', function (hooks) {
 
   module('with application and resolver set', function (hooks) {
     hooks.beforeEach(function () {
+      console.log('5', Ember.testing);
       setResolver(resolver);
       setApplication(application);
     });
@@ -863,6 +864,7 @@ module('setupContext', function (hooks) {
 
   module('with only resolver set', function (hooks) {
     hooks.beforeEach(function () {
+      console.log('6', Ember.testing);
       setResolver(resolver);
       setApplication(null);
     });