I have the following trigger on Contacts to send an email to one of our managers when a contact 'deactivated', however I don't know how to test the Messaging.SingleEmailMessage() code and my test covereage is not enough:

trigger InactiveNotificationTrigger on Contact (after update) {
    
    for (Contact c : Trigger.new){
        
        if(Trigger.oldMap.get(c.id).Record_Status__c == 'Active' && c.Record_Status__c == 'Inactive'){

            List<ID> ModID = New List<ID>();
            ModID.add(c.LastModifiedById);
            string FullEmailTxt;

            List<User> ModUser = [Select ID, name from user where ID in: ModID];
            for(integer i = 0 ; i < ModUser.size(); i++){
                string emailTxt1 = 'Dear Development and Communications Director, ';
                string emailtxt2 = 'The contact, '+c.FirstName+''+c.LastName+', has been marked inactive by '+ModUser[i].name+' on '+c.LastModifiedDate+'.'; 
                string emailTxt3 = 'To review the contact please follow the link: '+System.URL.getSalesforceBaseUrl().toExternalForm()+'/'+c.Id+'.'; 
                FullEmailTxt = emailTxt1+'\n'+'\n'+emailTxt2+'\n'+'\n'+emailTxt3+'\n'+'\n'+'Cheers!';
            }
            
    
            List<User> DevComMng = [Select ID, email from user where Title = 'DevComm Director'];
// for testing only List<User> DevComMng = [Select ID, email from user where Name = 'System Administrator'];
            for(integer i = 0 ; i < DevComMng.size(); i++){
                
                String[] toAddresses = new String[] {DevComMng[i].email};
                    
                Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
                email.setToAddresses(toAddresses);
                email.setSenderDisplayName('Salesforce Administration');
                email.setSubject('Inactive Contact Allert');
                email.setBccSender(false);
                email.setPlainTextBody(FullEmailTxt);
                email.setSaveAsActivity(false);
                Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});
                
            }
            
            Note n = new note();
                n.ParentID = c.id; n.Title = 'Inactive Notification Sent'; n.body = FullEmailTxt;
            insert n;
        }
    }
}

Here the test code I have now:
@isTest
private class TestInactiveNotificationTrigger {

    @isTest static void TestInactiveNotificationTrigger() {
        // Test data setup
        // Create a Board Campaign and assign and insert a current and former board member
        Contact con = new Contact(FirstName='Test',LastName='Contact');
        insert con;
        
        con.Status__c = 'Inactive';
//        con.Inactive_Reason__c = 'Deceased';
        update con;

        // Verify 
        // In this case the inserted contact record should have been updated as GRE Volunteer by the trigger,
        // so verify that we got back an empty search.
        List<ID> nID = New List<ID>();
        nID.add(con.id);
            List<Note> n = [SELECT id FROM Note WHERE ParentID in : nID];
            System.assert( (n.size() == 0), 'Notification Trigger failed.');
        
    }
}