PP-13107: Add instructions for requesting a Worldpay test account (#986)

* Adds instructions for requesting a Worldpay test account

* Added line about automated testing

* Minor fix

* Tidied up test account options

* Added sentence about making Worldpay test accounts a separate service

source/testing_govuk_pay/index.html.md.erb

@@ -49,6 +49,22 @@ Test data and API keys in your sandbox test account will not be available in you
 
 Stripe test accounts have [a different set of mock card numbers](#if-you-39-re-using-a-test-stripe-account).
 
+### Get a Worldpay test account
+
+It’s possible to link a Worldpay test account to GOV.UK Pay. Some services might find a Worldpay test account useful to connect GOV.UK Pay to Worldpay’s reporting products.
+
+For most organisations, a Worldpay test account is not necessary and we do not recommend using it. GOV.UK Pay cannot support you if you encounter problems.
+
+You can test the entire payment journey with a standard GOV.UK Pay test account, as well as:
+
+* reporting on payments
+* smoke testing
+* viewing and refunding transactions
+
+If you get a Worldpay test account, you should not use it for long term, automated testing.
+
+Email GOV.UK Pay support ([email protected]) to request a Worldpay test account. If GOV.UK Pay support approves your request, we will add your Worldpay test account as a separate GOV.UK Pay service.
+
 ## Testing your service
 
 You can use your test account to: