Paypal Sandbox How to Check Billing Plans and Billing Agreements

I've been building a subscription based on the REST API Billing plans and agreements using these sample codes from PayPal-PHP-SDK. However I can't seem to find the created billing plans and the billing agreements from my testings in sandbox and developer Paypal sites. Is there a way to check if the process was a success?

Here are my steps:

1. Create billing plan
2. Activate billing plan
3. Create Agreement based on active billing plan
4. Execute Agreement [Response was an Agreement Object with state = 'Active']