Debugging difficulties

Unit testing a serverless solution is fairly simple because any code that your functions rely on can be separated into modules and unit tested. Integration tests are a little bit more complicated because you need to be online to test using external services.

When it comes to debugging to test a feature or fix an error, it's a whole different problem. You can't hook into an external service to see how your code behaves step-by-step. Also, those Serverless APIs are not open sourced, so you can't run them in-house for testing. All you have is the ability to log steps, which is a slow debugging approach, or extract the code and adapt it to host into your own servers and make local calls.