private async Task ShouldCapturePayment_IdempotencyKey() { var captureResponse = new CaptureResponse(); _apiClient.Setup(apiClient => apiClient.Post <CaptureResponse>(PaymentsPath + "/payment_id/captures", _authorization, null, CancellationToken.None, "test")) .ReturnsAsync(() => captureResponse); IPaymentsClient paymentsClient = new PaymentsClient(_apiClient.Object, _configuration.Object); var response = await paymentsClient.CapturePayment("payment_id", null, "test"); response.ShouldNotBeNull(); }