# Fault injection

Abstract

How to use the Sitecore.Commerce.Plugin.FaultInjection plugin to test failure in a complex distributed solution.

Fault injection provides the ability to deliberately cause a service to fail, in order to test failure in a complex distributed solution. Sitecore XC has a single fault injection pattern, which covers the concurrency fault in the persistence of a Commerce Entity.

The Sitecore.Commerce.Plugin.FaultInjection plugin is included in the sample Commerce Engine project provided in the Sitecore.Commerce.Engine.SDK package.

To inject the defined concurrency fault:

1. Ensure that your Sitecore.Commerce.Engine project contains a reference to the Sitecore.Commerce.Plugin.FaultInjection.

2. In the API request, add a header named FaultInjection.

3. Assign the value ConcurrencyFault to the header you added in the previous step.

4. Invoke any API methods that persists a Commerce Entity.

At this point, you should have a concurrency fault raised.

The following is a sample result from calling the AddCartLine using Postman with the fault injection header inserted:

Content-Type:application/json

ShopName:{{ShopName}}

ShopperId:{{ShopperId}}

Language:{{Language}}

Currency:{{Currency}}

Environment:{{Environment}}

IpAddress:{{IpAddress}}

CustomerId:{{CustomerId}}

Roles:{{Roles}}

FaultInjection:ConcurencyFault

In Postman, the response body shows the following:

"ResponseCode": "Error",
"Messages": [
{
"MessageDate": "2016-09-01T12:12:45.0287079-05:00",
"Code": "Error"
"Text": "SQL.UpdateEntity.Fail:Id=Cart01|Try=1|Environment=Entity-CommerceEnvironment-
AdventureWorks|Message='Concurrency error: The Entity version supplied (1) is lower or equal to the current version
(1).'|Number=50000|Procedure='sp_CommerceEntitiesUpdate'|Line=22",
"CommerceTermKey": "EntityPersistException"
}