Apex Test Class

newbie here...thanks for your patience. I'm interested in writing a test class for the following controller, but not sure where to begin:

public class savecontroller
{
    private final Emp__c emps;
    public savecontroller(ApexPages.StandardController controller)
    {
        this.emps= (Emp__c)controller.getRecord();
    }
    public void autosave()
    {
        upsert emps;
    }   
}

Thank you