Write SOSL Queries Hands On Challenge

Kindly assist in this challenge. I have executed the ContactAndLeadSearch Class code successfully without errors  but encountered an error when Checking the Challenge though my debug window showed a successful compilation.

The problem and my debug window is shown below: 

Create an Apex class that returns both contacts and leads based on a parameter.

To pass this challenge, create an Apex class that returns both contacts and leads that have first or last name matching the incoming parameter.

• The Apex class must be called ContactAndLeadSearch and be in the public scope
• The Apex class must have a public static method called searchContactsAndLeads
  • The method must accept an incoming string as a parameter
  • The method should then find any contact or lead that matches the string as part of either the first or last name
  • The method should finally use a return type of List<List< sObject>>
• NOTE: Because SOSL indexes data for searching, you must create a Contact record and Lead record before checking this challenge. Both records must have the last name Smith. The challenge uses these records for the SOSL search