Testing APIs to ensure they are doing what they are supposed to be doing is essential. However, doing so only tells part of the story. How does your API behave when the API consumer makes a mistake? Learning how to consume an API can be hard, but it's even harder if it does not fail in expected ways. The HTTP specification defines a wide range of standard failure conditions. Does your API return the appropriate errors that will help the consumer fix or handle the error condition? This talk will discuss and demonstrate the types of tests you can run against your API to ensure it behaves as the consumer expects and make it as easy as possible for clients to be resilient to failure.