Say you are building a cloud app. Clearly, you will unit test the app during development to ensure it behaves the way you expect. And no matter how you develop your app, your favorite unit testing tool will make it easy to author, execute, and obtain results from your tests.
What about testing your app when you deploy it in a Kubernetes cluster (test/dev/staging/prod)? Does the app handle realistic load conditions with acceptable performance? Does the new version of the app improve business metrics relative to the earlier version? Is it resilient?