Kotlin coroutines are used to maintain a dozen non-trivial concurrent data structures, which need to be tested properly. Straightforward stress tests are unlikely to catch all possible bugs and flack periodically. The quality of such testing is below the bar. We need a way to write concurrent tests in a convenient, declarative way, keeping in mind “what” we are testing as opposed to “how” we are testing it. With this in mind, the Lincheck framework for writing concurrent tests was introduced. Users list all the data structure operations, and Lincheck verifies whether these operations are thread-safe. This talk presents Lincheck and explains how you can apply it to your setting while also giving a brief overview of the framework’s internals.