public async Task Fund_Wallet_Should_Return_Bad_Request_Response_When_Amount_Is_Less_Than_One() { //Arrange var fundWallet = new FundWalletRequestModel { Amount = 0 }; Mediator.Setup(x => x.Send(It.IsAny <FundWalletRequestModel>(), new CancellationToken())). Throws(new ArgumentException()); var walletController = new WalletController(Mediator.Object); //Action var result = await walletController.Fund(fundWallet); //Assert Assert.IsType <BadRequestObjectResult>(result); }