public async Task GetSaldoOk()
        {
            var serviceMock = new Mock <IContaService>();

            serviceMock.Setup(m => m.GetBalance(It.IsAny <Guid>())).ReturnsAsync(
                new ContaDtoBalance
            {
                Balance = 100
            }
                );

            _controller = new ContasController(serviceMock.Object);
            var result = await _controller.GetSaldo(Guid.NewGuid());

            Assert.True(result is OkObjectResult);
        }
        public async Task GetSaldoBadRequest()
        {
            var serviceMock = new Mock <IContaService>();

            serviceMock.Setup(m => m.GetBalance(It.IsAny <Guid>())).ReturnsAsync(
                new ContaDtoBalance
            {
                Balance = 100
            }
                );

            _controller = new ContasController(serviceMock.Object);
            _controller.ModelState.AddModelError("Id", "Formato Inválido");

            var result = await _controller.GetSaldo(Guid.NewGuid());

            Assert.True(result is BadRequestObjectResult);
        }