Async testing in Scala. We will start with common pitfalls in testing async code in the example of Scala Futures. We will show some examples of testing errors and negative cases, and using test doubles to simplify test code. Next, we will point out further support from ScalaTest to improve readability. After we have the basics down, we will walk through the example with cats to abstract away the use of Futures in the implementation. Finally, we will point to some exercises to learn more about the topic.