Some tests require or dont require the terminal to process an External Authenticate command.

The EXTERNAL AUTHENTICATE command asks the application in the ICC to verify a cryptogram which is present in EMV TAG 91 in the response.

External authentication is performed by the terminal if:

- AIP (Application Interchange Profile) indicates issuer authentication is supported. 

- Tag 91 is present in 0110/0210 message in DE55 field.

So if above conditions are met, irrespective of whether the response is an approval or decline, the external authentication should be performed.