public async Task CreateInvoiceItemTest() { // Arrange var args = new InvoiceItemCreateArguments(); _stripe.Post( Arg.Is <StripeRequest <InvoiceItemCreateArguments, InvoiceItem> >(a => a.UrlPath == "invoiceitems" && a.Model == args), _cancellationToken).Returns(Task.FromResult(new StripeResponse <InvoiceItem>())); // Act var response = await _client.CreateInvoiceItem(args, _cancellationToken); // Assert response.Should().NotBeNull(); }