public async void Should_UpdateMember()
        {
            UpdateMemberInput input = new UpdateMemberInput
            {
                UserName = "******",
                Member   = new MemberDto
                {
                    UserName = "******",
                    Name     = "Hess",
                    Surname  = "Johann",
                    IsMale   = true,
                    IsSingle = true // changed field
                }
            };

            var userOutput = await _userAppService.GetUsers();

            User   user     = _userRepository.FirstOrDefault(x => x.UserName == input.UserName);
            Member member   = _memberRepository.FirstOrDefault(m => m.UserName == input.UserName);
            long   userId   = user.Id;
            long   memberId = member.Id;

            DateTime?modificationTime = user.LastModificationTime;

            _memberAppService.UpdateMember(input);

            member = _memberRepository.Get(memberId);
            member.IsSingle.ShouldBe(true);

            user = _userRepository.Get(userId);
            // keine Änderung in User
            // user.LastModificationTime.ShouldBe(modificationTime);

            // Änderung des UserName bewirkt Änderung in Member und User
            input.Member.UserName = "******";
            _memberAppService.UpdateMember(input);

            member = _memberRepository.Get(memberId);
            member.UserName.ShouldBe(input.Member.UserName);

            user = _userRepository.Get(userId);
            user.UserName.ShouldBe(input.Member.UserName);
        }