public void TestClientControllerDoesNotAddClientWhenClientExists()
        {
            clientRepoMocked.Setup(x => x.FindByUsername("ExistingClient")).Returns(() => new Client());

            ClientController controller = new ClientController(clientRepoMocked.Object);
            ClientViewModel  client     = new ClientViewModel()
            {
                Username = "******",
                Password = "******"
            };

            controller.AddOrEdit(client);

            Assert.AreEqual(nrCurrentClienti, nrInitialClienti);
        }