Testing Angular with TsMocks and TestBed

testing.spec.ts

import { TestBed, inject } from '@angular/core/testing';

import { Mock } from 'ts-mocks';
import { MainService } from './main.service';
import { SubService } from './sub.service';

describe('MainService using useValue', () => {
  let mockService: Mock<SubService>;
  let systemUnderTest: MainService;

  beforeEach(() => {
    mockService = new Mock<SubService>({ getSomeValue: () => 'fake value' });

    TestBed.configureTestingModule({
      providers: [
        MainService,
        { provide: SubService, useValue: mockService.Object}
      ]
    });

    systemUnderTest = TestBed.get(MainService);
  });

  it('should return value from mocked subService', () => {
    // No extra mocking should return initial value
    expect(systemUnderTest.getSubValue()).toBe('fake value');
  });

  it('should return another value from mocked subService', () => {
    mockService.extend({ getSomeValue: () => 'fake another value'});

    expect(systemUnderTest.getSubValue()).not.toBe('fake another value');
  });
});

describe('MainService using useFactory', () => {
  let mockService: Mock<SubService>;
  let systemUnderTest: MainService;

  beforeEach(() => {
    mockService = new Mock<SubService>({ getSomeValue: () => 'fake value' });

    TestBed.configureTestingModule({
      providers: [
        MainService,
        { provide: SubService, useFactory: () => mockService.Object}
      ]
    });

    systemUnderTest = TestBed.get(MainService);
  });

  it('should return value from mocked subService', () => {
    // No extra mocking should return initial value
    expect(systemUnderTest.getSubValue()).toBe('fake value');
  });

  it('should return another value from mocked subService', () => {
    mockService.extend({ getSomeValue: () => 'fake another value'});

    expect(systemUnderTest.getSubValue()).toBe('fake another value');
  });
});