What are the tests for sertraline overdose?

There Aren't Any. Sertraline overdose is seldom fatal. Emergency care is symptomatic --- in other words, if the person is nauseous, we give something for that, if they vomit & become dehydrated, we give fluids, & so on. You can take a sertraline level but, unless it's zero, that won't tell you what to do clinically.