Testing Strategy Code

ExampleClass.cls

public static String uppercase(String name) {
    if (name == null) {
        return 'NULL';
    }
    
    if (name.trim() == '') {
        return 'BLANK';
    }
    
    return name.toUpperCase();
}

ExampleTrigger.cls

Trigger SkipStatusCalled on Lead (before insert, before update) {
    for (Lead lead : Trigger.new) {
        if (
            lead.Called__c &&
            lead.Status == 'Open - Not Contacted'
        ) {
            lead.Status = 'Working - Contacted'
        }
    }
}