This particular Sandbox guide is intended to support developers who are integrating with the PayPal Here SDK.
The Sandbox enables you to test in a safe environment before moving your app into production. When you initiate a transaction in the Sandbox, PayPal creates a mock transaction. Sandbox transactions are tracked on the Sandbox site (https://www.sandbox.paypal.com), as live transactions are tracked on the live site (https://www.paypal.com).
After you create Sandbox accounts, you can log into the Sandbox with the username and password from one of your test accounts and review the status of the mock transactions associated with an account.
Note: Some rules for processing credit cards are not triggered in the Sandbox. Therefore, some credit card transactions that are successful in the Sandbox may be unsuccessful in production.
PayPal doesn't provide a set of test payment cards. Many developers obtain and test with prepaid credit cards. However, if you would like to test keyed entry payments, you can use test cards that are generated at step 4 of this support page.