Kotlin was the rising star of programming languages in 2016. It not only became final with version 1.0 but also got rapidly adopted in the android community. But many companies are struggling to add Kotlin to an existing Java project. It's not easy to add a new language to an existing team. But it's much easier to introduce Kotlin to your project using the backdoor: your unit tests. So let's look at Kotlin more from a testing perspective. How does it look like to write tests in Kotlin, what possibilities of the language will help us?