it('should save user', () => {
      const expectedUser = {
        id: 7,
        firstName: 'Grzegorz',
        lastName: 'Pluta',
        email: 'grzegorz.pluta@gmail.com',
        login: 'gpluta',
        password: 'gpluta',
        role: 'user'
      };

      userService.addUser(expectedUser).subscribe(
        user => expect(user.firstName).toEqual('Grzegorz', 'first name should be equal'),
      );

      const req = httpTestingController.expectOne(userService.userUrl);
      expect(req.request.method).toEqual('POST');

      req.flush(expectedUser);
    });