example-test.js

import pause from './helpers/pause';

test("fooo", async () => {
  
  await visit('/foo');
  
  await pause(); // will pause here, but can be resumed by typing `resume`
  await click('#bar');
  
  // some assertions
})

pause-test.js

let resolve;

Object.defineProperty(self, 'resume', {
	get() {
		if (resolve) {
			console.log('resuming...');

			resolve();
			resolve = undefined;
		} else {
			throw TypeError('nothing paused to resumt')
		}
	}
})
export default async function pause() {
	if (resolve) {
		throw TypeError('already paused')
	}
	console.log(`test "${QUnit.config.current.testName}" paused. (type "resume" to continue)`, QUnit.config.current.callback);

	return new Ember.RSVP.Promise(_resolve => resolve = _resolve);
}

someone should maybe consider submitting this as an addition to the existing test helpers.