In order for you to test Oxxo Pago en efectivo payment method successfully, you don’t need any given test data.
Oxxo Pago en efectivo Payment Flow
The customer enters the required details: email address, first name and last name.
The customer receives a voucher with a barcode. In order to complete the payment, he needs to print the voucher with the barcode and pay it at any Oxxo store.