As a part of the integration test I would like to check for a specific error/warn/info/debug-message to be present (or not present) in the log.

I can think of two possible implementation approaches:

1. Implement a method that returns the log, e.g. as an array of log messages or log objects (logLevel, timestamp, message) or just the whole dump as string - whichever is easier to implement, though an array of log objects would be the most useful option from a developer side of view.
2. Implement a method that checks the log for containing a specific Regex with a specific log level.

Use case

During fixing a bug in my adapter I have introduced a follow-up-bug that can be identified by a specific log message. To fix this bug I would like to implement a test case that checks for this specific log message.