app.component.spec.ts

import { TestBed, async } from '@angular/core/testing';
import { RouterTestingModule } from '@angular/router/testing';
import { AppComponent } from './app.component';
import { getTranslocoModule } from './transloco-testing.module';

describe('AppComponent', () => {
  beforeEach(async(() => {
    TestBed.configureTestingModule({
      imports: [
        getTranslocoModule(),
        RouterTestingModule,
      ],
      declarations: [
        AppComponent
      ],
      providers: []
    }).compileComponents();
  }));

  it('should create the app', () => {
    const fixture = TestBed.createComponent(AppComponent);
    const app = fixture.componentInstance;
    expect(app).toBeTruthy();
  });


  it('should render title', () => {
    const fixture = TestBed.createComponent(AppComponent);
    fixture.detectChanges();
    const compiled = fixture.nativeElement;
    console.log(compiled);
    expect(compiled.querySelector('h1').textContent).toContain('Русский заголовок');
  });
});

transloco-testing.module.ts

import {
  TranslocoConfig,
  TranslocoTestingModule
} from '@ngneat/transloco';
import en from '../assets/i18n/en.json';
import ru from '../assets/i18n/ru.json';


export function getTranslocoModule(config: Partial<TranslocoConfig> = {}) {
  return TranslocoTestingModule.withLangs({ en: en, ru: ru }, { availableLangs: ['en', 'ru'],  defaultLang: 'ru' });
}