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

# Usage

> Generate test cards, trigger sandbox errors, and fill payment forms

## Open the sidebar

Select the Payment Sandbox Helper toolbar icon. Chrome opens the extension in a side panel; Firefox opens its sidebar panel. Keeping the panel visible makes it easier to test several checkout states without repeatedly reopening the extension.

## Test a PayPal Sandbox checkout

<Steps>
  <Step title="Open a supported sandbox page">
    Navigate to PayPal Sandbox, a supported local development page, or an App Engine test application containing a card form.
  </Step>

  <Step title="Choose the PayPal section">
    Select the required card network, or choose a PayPal error trigger for a negative test case.
  </Step>

  <Step title="Generate or select test data">
    The extension provides a card number, future expiry date, and matching three- or four-digit CVV.
  </Step>

  <Step title="Fill the form">
    Use the fill action to populate detected card fields, then review every value before submitting the sandbox payment.
  </Step>
</Steps>

### PayPal error triggers

Available scenarios include card refused, suspected fraud, expired card, invalid card data, insufficient funds, lost or stolen card, invalid account, generic decline, and CVV failure.

<Warning>
  Error triggers are provider-specific test values. Their behavior depends on PayPal Sandbox and may change independently of the extension.
</Warning>

## Test Stripe scenarios

The Stripe section groups predefined test cards by expected behavior:

* **Success** — standard successful card-payment scenarios.
* **Decline** — cards intended to produce declined-payment responses.
* **3D Secure** — authentication and challenge scenarios.

Select the scenario that matches the application path being tested, then fill or copy the card data into the Stripe test form.

## Fill a complete card form

The automatic fill action attempts to identify common fields for:

* Card number.
* Combined expiry or separate month/year controls.
* CVV, CVC, or security code.
* Cardholder name.
* Billing country input or select field.

The helper dispatches normal `input` and `change` events so React and other frontend frameworks can detect the inserted values.

## Fill one field with the context menu

<Steps>
  <Step title="Focus or right-click an input">
    Select the field that should receive test data.
  </Step>

  <Step title="Open the browser context menu">
    Right-click and choose a Payment Sandbox Helper action.
  </Step>

  <Step title="Select a value">
    Choose the required card or field value. The extension inserts it into the last focused input.
  </Step>
</Steps>

## Configure defaults

Open the settings view to configure:

* Default billing country.
* Default cardholder name.
* PayPal and Stripe card background images.
* English or Vietnamese interface language.

Preferences are saved in browser extension storage.

## When automatic fill does not work

Some payment providers render sensitive inputs inside isolated cross-origin iframes. The browser may prevent the content script from reaching those fields. In that case, copy the values from the sidebar and paste them manually. Also verify that the page is on a supported hostname and that its field markup has not changed.


## Related topics

- [ePlus.DEV Browser Extensions](/index.md)