Add test for Logger.debug

[lacinoire]

Hey 😊 I want to contribute the following test:

Test that calling Logger.getLogger(LoggerTest.class).debug("debug message") does not throw an exception. This tests the method Logger.debug. This test is based on the test logger.

Curious to hear what you think!

(I wrote this test as part of a research study at TU Delft. Find out more)