title: How are test credit card numbers standardized?
body: <p>Looking through documentations of various payment processors such as Stripe and PayPal, I've noticed there are quasi-universal test credit card numbers e.g. <code>4111 1111 1111 1111</code>, <code>4242 4242 4242 4242</code>, <code>5555 5555 5555 4444</code>, etc[1][2]. I'd like to learn about the rules behind them.</p>
  <ul>
  <li>Are those test card numbers predefined standards or are they just conventional?</li>
  <li>Is it OK for a payment service provider (PSP) to make up one?
  <ul>
  <li>If so, how should a PSP define a mock card without coinciding with a genuine card?</li>
  <li>Are there any PAN ranges reserved universally for test/mock purposes?</li>
  </ul>
  </li>
  </ul>
  <p>I don't have full access to the proprietary ISO/IEC 7812, which could be what I'm missing.</p>
  <p>References</p>
  <ul>
  <li>[1] Test your integration <a href="https://stripe.com/docs/testing" rel="nofollow noreferrer">https://stripe.com/docs/testing</a></li>
  <li>[2] Test Transactions card number <a href="https://developer.paypal.com/docs/payflow/integration-guide/test-transactions/" rel="nofollow noreferrer">https://developer.paypal.com/docs/payflow/integration-guide/test-transactions/</a></li>
  </ul>