If you do have an EziDebit test account, then please note the amounts has the be in whole dollars. If it is not whole numbers i.e decimal which shows cents in an amount, then this will lead to failed payments for Visa and Master card.
Please see the testing notes from the EziDebit website: "Our sandbox environment allows you to test failed and successful payments for Visa and MasterCard depending on what number you enter for the number of cents in the payments amount. Zero cents (e.g. 100 or 100.00) will always be successful. Any other number of cents will always fail with the failed reason corresponding to the number of cents (e.g. 100.51 as the payment amount will fail with error code 51, meaning insufficient funds)."
Note: Features of tax, cover transaction fee etc give the amount as dollars and cents therefore can cause issue with ezidebit sandbox environment.