❗️
Never Use Real Data
Never use real credit card or bank account information when testing.
The gateway provides several methods for testing transactions without sending any data to the credit card or ACH processor.

Sandbox Account

How it works

Log in to guide.nmi.com to retrieve Sandbox Keys or access the Sandbox Partner and Merchant Portals.
Build and test your integration.
All transactions are simulated; no charges are processed.

Best for

Full integration testing before going live.
Safe development without impacting production accounts.

Test Transaction

How it works

Set test_mode to "enabled" on a single transaction.
Use one of the Test Credit Card Numbers with expiration date 10/29.
Processes only that transaction in test mode; all other account transactions remain normal.

Example

{
  "security_key": "your_live_key",
  "test_mode": "enabled",
  "ccnumber": "4111111111111111",
  "ccexp": "1025"
}

Best for

Testing in a development environment while your live site processes real transactions.
Quickly validating a specific payment scenario.

Notes

Only available on live accounts (not supported in Sandbox).
To view in reporting, temporarily toggle account to test mode.

Demo Account

How it works

Use the Payment Gateway Demo Account — always available, no setup required.
Security key:

6457Thfj624V5r7WUwc5v6a68Zsd6YEm

Completely isolated from your own accounts.

Best for

Quick tests, training sessions, or demos.
Shared testing between teams or external partners.

Notes

Fully sandboxed—no actual processing occurs.
Safe to embed in code samples or documentation.

Test Mode

How it works

Toggle any merchant account into test mode.
All valid credit cards will be “approved” without actual charges or processing.

Best for

Testing all transactions in a controlled environment.
Bulk or repeated tests.

Notes

While in test mode, all transactions are simulated.
Avoid enabling in a live production environment serving customers.

Test Values

Card and ACH

Card Type	Number
Visa	4111111111111111
MasterCard	5431111111111111
Discover	6011000991300009
American Express	341111111111111
Diner’s Club	30205252489926
JCB	3541963594572595
Maestro	6799990100000000019

Other Details	Value
Credit Card Expiration	10/29
Account (ACH)	24413815
Routing (ACH)	490000018

Triggering Specific Responses

Goal	How to Trigger
Declined transaction	Amount less than `1.00`
Fatal error	Invalid card number
AVS match	Address1 = `888`, Zip = `77777`
CVV match	CVV = `999`

3D Secure (3DS) in Sandbox

Not Enrolled – Frictionless Flow

Cards return Enrolled: "N", skipping authentication.

Card Type	Number
Visa	4111111111111111
Mastercard	5431111111111111
Amex	341111111111111
Discover	6799990100000000019

Expected:

cardholder_auth: "attempted"
CAVV: (empty)
ECIFlag: "07" (Not enrolled)

Frictionless Authentication Flow

Cards return Enrolled: "Y" with CAVV present.

Card Type	Number
Visa	4100000000000100
Mastercard	5100000000000107
Amex	340000000000108
Discover	6440000000000104

Expected:

cardholder_auth: "verified"
CAVV: "mock_cavv_0002_1234567890"
ECIFlag: "05" (Authenticated)

Challenge Flow

Triggers a 3DS challenge with mock interaction.

Card Type	Number
Visa	4100000000005000
Mastercard	5100000000005007
Amex	340000000005008
Discover	6440000000005004

Expected:

Enrolled: "Y"
PAResStatus: "C" (Challenge required)
ECIFlag: "02" (Challenge required)
User sees a mock challenge interface.

Challenge Actions

Result	Action
Pass	Enter code `12345`
Fail	Enter any other code
Cancel	Close the challenge