I am looking for a way to modify catch block depending on if it's executed during the unit test run or not. The purpose is basically to detect/setup mock expectations which are swallowed because catch doesn't rethrow. I am using MSTest. One obvious thing is using preprocessor but I don't think it works. Especially if to use DEBUG define. There should be an easy way to detect that, shouldn't it? I must have been looking for something wrong because I couldn't find much info on that. try {...} catch(Exception) { Log(...); #if DEBUG throw; #endif }