Here is the code for auto populate account on lead when the email domain match. Can pls someone let me know test class for this class

public static void handleBeforUpdate() 
    {
        Set<String> leadEmails = new Set<String>();
        Map<String,Id> conmap = new Map<String,Id>();
        List<Lead> vLstLead = new List<Lead>();

    for(Lead l :(List<Lead>)trigger.new){

        if(!l.IsConverted && null != l.email && '' != l.email)
            leadEmails.add(l.Lead_s_email_domain__c);
    }

    Set<String> contactEmailMatches = new Set<String>();
    
    List<Contact> conList = [SELECT Id,Accountid,Email,Contact_s_email_domain__c From Contact where Contact_s_email_domain__c IN :leadEmails];
   
    if(conList != null) {
    for(Contact c : conList) {
        contactEmailMatches.add(c.Contact_s_email_domain__c);
        conmap.put(c.Contact_s_email_domain__c, c.accountId);
       }
    }
  

    for(Lead l :(List<Lead>)trigger.new){

        if(!l.IsConverted){
         if(contactEmailMatches.contains(l.Lead_s_email_domain__c) && !l.is_domain_matched__c){
                l.is_domain_matched__c = True;
                l.AccountName__c = conmap.get(l.Lead_s_email_domain__c);
             }
            }
        }
    }

}