Hi, I already have working my PayPal buttons working, now I want to do some negative testing. I already activate the negative testing option in my business account. I decided to use the request headers to try to receive the mock responses. This is my code to set the header. Option 1 IEnumerable<string> enumHeaders = new List<string>() { "mock_application_codes", "DUPLICATE_INVOICE_ID" }; request.Headers.Add("PayPal-Mock-Response", enumHeaders); Option 2 request.Headers.Add("PayPal-Mock-Response", "{'mock_application_codes':'DUPLICATE_INVOICE_ID'}"); Option 3 request.Headers.Add("PayPal-Mock-Response", "DUPLICATE_INVOICE_ID"); Finally executing this piece of code request.RequestBody(orderRequest); and it breaks. Anyone could point me in the right direction to get my negative testing working. Thanks Alberto
... View more