`isTesting` from `@embroider/macros` returns false in tests if `ember-classic-decorator` is a devDependency

[mrloop]

I've a minimal reproduction here https://github.com/mrloop/em-user-activity initially thought it was ember-user-activity causing the issue but it depends on ember-classic-decorator and the issue occurs with just ember-classic-decorator declared as a devDependency.

In the demonstration app the following test passes when ember-classic-decorator is not used.

import { module, test } from 'qunit';
import { setupTest } from 'my-data/tests/helpers';
import { isTesting } from '@embroider/macros';

module('Unit | Controller | isTesting', function (hooks) {
  setupTest(hooks);

  test('it exists', function (assert) {
    assert.true(isTesting(), 'isTesting should be true');
  });
});

When ember-classic-decorator is installed isTesting() returns false in the test.

[bartocc]

Took me quite a while to get to the same conclusion @mrloop!

To give a bit more context, this issue happens when using a combinasion of ember-data@4.5+ AND ember-classic-decorator@3.0.1+.

I hit this issue while upgrading or app from ember-data@4.3.0 to ember-data@4.5.0. To be more precise, the first ember-data release causing the issue is ember-data@4.4.0-alpha.8. And our app also uses ember-classic-decorator@3.0.1…

Looks like ember-classic-decorator is causing the require of module @embroider/macros/runtime

At the end of this module, we do

  let updaters = typeof window !== 'undefined' ? window._embroider_macros_runtime_config : undefined;
  if (updaters) {
    let methods = updaterMethods();
    for (let updater of updaters) {
      updater(methods);
    }
  }

But window._embroider_macros_runtime_config is not set yet
=> so we don't enter the if
=> we don't run any updater
=> we don't set isTesting to true

[bartocc]

Here's a repo with a bare ember app + ember-classic-decorator@3.0.1 and ember-data@4.4.0-alpha.8 and a test to reproduce.

https://github.com/bartocc/ember-classic-decorator-issues-99