ember-test never terminates with COVERAGE=true

close-mirage.js

// tests/helpers/close-mirage.js

export function closeMirage(hooks) {
  hooks.afterEach(function () {
    if (window.server) { // close Mirage Server if present
      window.server.shutdown();
    }
  });
}

component-test.js

// tests/integration/modules/components/custom/custom-button

import { module, test } from 'qunit';
import { setupRenderingTest } from 'ember-qunit';
import { render } from '@ember/test-helpers';
import { closeMirage } from 'PROJECT-NAME/tests/helpers/close-mirage'; // change PROJECT-NAME
import hbs from 'htmlbars-inline-precompile';

module('Integration | Component | custom/custom button', function(hooks) {
  setupRenderingTest(hooks);
  closeMirage(hooks); // <-- closing mirage via common helper

  test('it renders', async function(assert) {
    // ...
  });
});