import { asap } from 'rxjs/scheduler/asap';

export class TestClass {
  complete = false;
  doSomethingAsap() {
    asap.schedule(() => {
      this.complete = true;
    });
  }
}

import { fakeAsync, tick } from '@angular/core/testing';
import { TestClass } from './test-class';

describe('TestClass', () => {
  it('should do stuff asynchronously', fakeAsync(() => {
    // arrange
    const test = new TestClass();

    // act
    test.doSomethingAsap();

    tick();

    // assert
    expect(test.complete).toBeTruthy();
  }));
});