That depends on your business requirements. If there are specific, measurable business requirements for LOGGING in your application, then yes, it should be tested. If not, as in the case of most applications, logging should probably be used simply for what it is, a diagnostic tool. I use logging to help me build my tests by redirecting my logging to the Test Context using a TestContext Logging Provider that I wrote, and which can be seen in the sample code for my .NET TDD Kickstart session. This ALLOWS me to use my logging to help develop the system, GIVES me insight into how the logging will look when I actually use the system, and doesn't require me to make-up any fake "requirements" for logging. By the way, if anyone knows of any specific, testable requirements for logging other than, "...the system must LOG something…",

That depends on your business requirements. If there are specific, measurable business requirements for logging in your application, then yes, it should be tested. If not, as in the case of most applications, logging should probably be used simply for what it is, a diagnostic tool. I use logging to help me build my tests by redirecting my logging to the Test Context using a TestContext Logging Provider that I wrote, and which can be seen in the sample code for my .NET TDD Kickstart session. This allows me to use my logging to help develop the system, gives me insight into how the logging will look when I actually use the system, and doesn't require me to make-up any fake "requirements" for logging. By the way, if anyone knows of any specific, testable requirements for logging other than, "...the system must log something…",