Overview
This guide explains how to test the MPGS gateway safely using sandbox credentials and WHMCS Gateway Logs.
Step 1 – Enter Sandbox Credentials
Your bank (or MPGS portal) should provide a test Merchant ID and API Password. Enter these under:
System Settings → Payments → Payment Gateways → MPGS
Step 2 – Enable Debug Logging (Temporary)
Enable Debug Logging in the MPGS gateway configuration.
Logs can be viewed at:
Utilities → Logs → Gateway Log
Step 3 – Run Test Scenarios
We recommend testing each of the following:
- Client checkout: Pay an invoice using a new card (CVV provided)
- Stored card charge: Pay an invoice using card on file
- Admin charge: Attempt to capture payment from the admin invoice screen (if used)
- Refund: Full and partial refund tests
- Cron simulation: Trigger automation (or use a due invoice) to confirm recurring billing behaviour
Important: Stored Cards and CVV
WHMCS does not store CVV (Card Security Code). CVV is only available when the user enters it during checkout.
This means recurring and cron charges must be processed as merchant-initiated recurring transactions where supported by your merchant profile.
Common Test Errors
| Error | Meaning | Fix |
|---|---|---|
| Card security code (CVV) is required. | Gateway is requiring CVV for this transaction type. | Ensure recurring / merchant-initiated transactions are enabled by your bank OR ensure the transaction is being submitted as recurring (see Going Live guide). |
| HTTP 401 Unauthorized | Credentials/username format incorrect. | Confirm Merchant ID and API Password. Username should be merchant.{MerchantID}. |
| HTTP 400 / Unexpected parameter | Payload does not match your API version. | Confirm API Version (commonly 100) and required payload fields. |
Step 4 – Disable Debug Logging
Once testing is complete, turn Debug Logging OFF to reduce log volume and risk.