> ## Documentation Index
> Fetch the complete documentation index at: https://developer.pagou.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Testing and Troubleshooting

> Validate Payment Element in sandbox, test 3DS paths, and diagnose the most common integration mistakes.

Use this page before launch and whenever browser payment behavior looks inconsistent.

<Note>
  For the sandbox test cards, documents, and amounts that drive each outcome (approved, declined, 3DS
  challenge/frictionless, tokenization, and Pix/Boleto settlement), see [Test Data](/start-here/test-data).
</Note>

## Test checklist

* confirm the browser uses the sandbox public key
* confirm the backend uses the sandbox secret token
* verify the backend returns the transaction payload intact
* verify webhook delivery before trusting browser state
* reconcile any interrupted 3DS attempt

## Example backend request

```json theme={null}
{
  "external_ref": "order_2001",
  "amount": 2490,
  "currency": "BRL",
  "method": "credit_card",
  "token": "pgct_token_from_browser"
}
```

## Example backend response

```json theme={null}
{
  "success": true,
  "requestId": "0190a2b4-18a7-7de0-9a43-69b7cf261201",
  "data": {
    "id": "018f1f2e-7b43-7c9a-8d3e-1a2b3c4d5e70",
    "status": "pending"
  }
}
```

## Common error

```json theme={null}
{
  "type": "https://api.pagou.ai/problems/validation-error",
  "title": "Validation Error",
  "status": 422,
  "detail": "The request contains invalid data.",
  "errors": [
    {
      "field": "token",
      "message": "Token is required for credit card payments",
      "code": "invalid_type"
    }
  ]
}
```

Fix: if the backend cannot see a valid Payment Element token, stop and verify the browser integration before changing order logic or webhook handling.