CustomerID registration offers many configuration parameters but to get started in testing you only need few.
eidm2.properties
registration.1 = person
registration.1.enabled = true
registration.1.methods = { "name" : "password.2", "mandatory" : "true", "visible" : "false", "default" : "true" }
registration.1.userinfo.fields = {acceptTerms}, {firstname, surname, customerid, email, password}
registration.1.summary.fields = firstname, surname, customerid, email
registration.1.organizations = { "path" : "all_users", "organizationtype" : "users" }
registration.1.roles = [ "all_users/User"]
Make sure you define the organization where the user should be created with key registration.N.organizations.