Angular 4 Unit Tests (TestBed) extremely slow

describe('Test name', () => {
    configureTestSuite();

    beforeAll(done => (async () => {
       TestBed.configureTestingModule({
            imports: [HttpClientTestingModule, NgReduxTestingModule],
            providers: []
       });
       await TestBed.compileComponents();

    })().then(done).catch(done.fail));

    it(‘your test', (done: DoneFn) => {

    });
});

Create new file:

    import { getTestBed, TestBed, ComponentFixture } from '@angular/core/testing';
    import { } from 'jasmine';

    export const configureTestSuite = () => {
       const testBedApi: any = getTestBed();
       const originReset = TestBed.resetTestingModule;

       beforeAll(() => {
         TestBed.resetTestingModule();
         TestBed.resetTestingModule = () => TestBed;
       });

       afterEach(() => {
         testBedApi._activeFixtures.forEach((fixture: ComponentFixture<any>) => fixture.destroy());
         testBedApi._instantiated = false;
       });

       afterAll(() => {
          TestBed.resetTestingModule = originReset;
          TestBed.resetTestingModule();
       });
    };

It turned out the problem is with Angular, as addressed on Github

Below a workaround from the Github discussion that dropped the time for running the tests from more than 40 seconds to just 1 second (!) in our project.

const oldResetTestingModule = TestBed.resetTestingModule;

beforeAll((done) => (async () => {
  TestBed.resetTestingModule();
  TestBed.configureTestingModule({
    // ...
  });

  function HttpLoaderFactory(http: Http) {
    return new TranslateHttpLoader(http, "/api/translations/", "");
  }

  await TestBed.compileComponents();

  // prevent Angular from resetting testing module
  TestBed.resetTestingModule = () => TestBed;
})()
  .then(done)
  .catch(done.fail));