Hello every one. can any one tell me how to write test class.
this is my code, i want to write test class

public class receipt80g{

   public receipt80g(ApexPages.StandardController controller) {
    
    List<Donation_Detail__c> donation=[select Donor__r.name,Bank_Name__c,Branch__c,Cheque_No__c,Amount__c,Mode_of_Payment__c,Date_of_Donation__c from Donation_Detail__c];
   
     }
}

thanks in advance.

When checking the challenge I get this message:

Challenge Not yet complete... here's what's wrong: 
There was an unexpected error while verifying this challenge. Usually this is due to some pre-existing configuration or code in the challenge Org. We recommend using a new Developer Edition (DE) to check this challenge. If you're using a new DE and seeing this error, please post to the developer forums and reference error id: AUWFEJSU

What exactly is causing this error?

Is Salesforce CPQ a part of sales cloud

Having a nightmare with the above section in the Process Automation module - Confident I've completed things correctly but I keep getting the same message when checking the challenge "The 'Case Escalate on High Priority' Workflow rule was not found. Either it was not created, not associated with Case, or not activated" 

Any help here? I've activated the rule and it all looks good from my side *scratching head*