chore(internal): add tests for enable/disable inertness

Author: NullVoxPopuli

tests/unit/inert-test.js

@@ -0,0 +1,29 @@
+import { module, test } from 'qunit';
+import { setupTest } from 'ember-qunit';
+
+import { macroCondition, dependencySatisfies } from '@embroider/macros';
+
+module('Unit | inert', function (hooks) {
+  setupTest(hooks);
+
+  function hasPolyfill() {
+    let initializers = ['install-function-helper-manager', 'usable-function-manager'];
+
+    return Object.keys(window.requirejs.entries).some(e => initializers.some(name => e.includes(name)))
+  }
+
+  if (macroCondition(dependencySatisfies('ember-source', '4.5.0-alpha.3'))) {
+
+    test('polyfill is inert', function(assert) {
+      assert.strictEqual(hasPolyfill(), false, 'no polyfill');
+    });
+
+  } else {
+
+    test('polyfill is present', function(assert) {
+      assert.strictEqual(hasPolyfill(), true, 'has polyfill');
+    });
+
+  }
+
+});