public async Task CreateRefundTest() { var args = new RefundCreateArguments { ChargeId = "some-value" }; _stripe.Post( Arg.Is <StripeRequest <RefundCreateArguments, Refund> >( a => a.UrlPath == "refunds" && a.Model == args), _cancellationToken) .Returns(Task.FromResult(new StripeResponse <Refund>())); var response = await _client.CreateRefund(args, _cancellationToken); response.Should().NotBeNull(); }